Answer:
a = -8
Step-by-step explanation:
-5/2 a + 5 = 25
Subtract 5 from each side
-5/2 a + 5-5 = 25-5
-5/2 a = 20
Multiply each side by -2/5
-2/5 *-5/2 a = 20*-2/5
a = -8
URGENT PLZ HELP THANK YOU!
Answer:
[tex](-5)^{11}[/tex]
Step-by-step explanation:
We can use the exponent rules. If we have [tex]\frac{a^b}{a^c}[/tex], then it will simplify to [tex]a^{b-c}[/tex].
b is 5, c is -6, and a is -5 so:
[tex]-5^{5-(-6)}\\-5^{11}[/tex]
Hope this helped!
All the edges of a cube have the same length. Tony claims that the formula SA = 6s, where s is the length of
each side of the cube, can be used to calculate the surface area of a cube.
a. Draw the net of a cube to determine if Tony's formula is correct.
b. Why does this formula work for cubes?
Frances believes this formula can be applied to calculate the surface area of any rectangular prism. Is
she correct? Why or why not?
d. Using the dimensions of Length, Width and Height, create a formula that could be used to calculate the
surface area of any rectangular prism, and prove your formula by calculating the surface area of a
rectangular prism with dimensions L = 5m, W = 6m and H=8m.
Answer:
Here's what I get
Step-by-step explanation:
a. Net of a cube
Fig. 1 is the net of a cube
b. Does the formula work?
Tony's formula works if you ignore dimensions.
There are six squares in the net of a cube.
If each side has a unit length s, the total area of the cube is 6s.
c. Will the formula work for any rectangular prism?
No, because a rectangular prism has sides of three different lengths — l, w, and h — as in Fig. 2.
d. Area of a rectangular prism
A rectangular prism has six faces.
A top (T) and a bottom (b) — A = 2×l×w
A left (L) and a right (R) — A = 2×l×h
A front (F) and a back (B) — A = 2×w×h
Total area = 2lw + 2lh + 2wh
If l = 5 m, w = 6 m and h = 8 m,
[tex]\begin{array}{rl}A &=& \text{2$\times$ 5 m $\times$ 6 m + 2$\times$ 5 m $\times$ 8 m + 2 $\times$ 6 m $\times$ 8 m}\\&=& \text{60 m}^{2} + \text{80 m}^{2} + \text{96 m}^{2}\\&=& \textbf{236 m}^{2}\\\end{array}[/tex]
At the Olympic games, many events have several rounds of competition. One of these events is the men's 100 100100-meter backstroke. The upper dot plot shows the times (in seconds) of the top 8 88 finishers in the final round of the 2012 20122012 Olympics. The lower dot plot shows the times of the same 8 88 swimmers, but in the semifinal round. Which pieces of information can be gathered from these dot plots? (Remember that lower swim times are faster.) Choose all answers that apply: Choose all answers that apply:
Answer:
The center of the semifinal round distribution is greater than the center of final round distribution.
The variability in the semifinal round distribution is less than variability in the final round distribution.
Step-by-step explanation:
The mean value of each distribution set is not calculates as the center of semifinal round distribution is greater than the final round distribution. MAD Mean Absolute Deviation is calculated from the dotted graph plot, the distribution of semifinal round is less spread out than the final round distribution.
Answer:
correct answer is None of the above i understood nothing the other person was trying to say...
Step-by-step explanation:
mark me brainliest please...
8 kids bought a 3 cakes. How many equal parts will need to divide it so that everyone can have it. Easy one!
Answer:
3/8 is your answer.
Step-by-step explanation:
Given:
8 kids bought a 3 cakes.
Required:
How many equal parts will need to divide it so that everyone can have it.
Solution:
3/8
Hope this helps ;) ❤❤❤
Reduce 5/15 to its lowest terms
Answer:
The answer is 1/3
Answer:
1/3
Step-by-step explanation:
The factors of 5 are 1,5;
* The factors of 15 are 1,3,5,15.
We can see that the GCD is 5 because it is the largest number by which 5 y 15 can be divided without leaving any residue.
To reduce this fraction, simply divide the numerator and denominator by 5 (the GCF).
So, 5 /15
= 5÷5 /15÷5
= 1 /3
There are 9 classes of 25 students each, 4 teachers, and two times as many chaperones as teachers.
Each bus holds a total of 45 people.
What is the least number of buses needed for the field trip?
5 buses is the answer pls mark me brainliest
Least number of bus require for trip = 5 buses
What is Unitary method?It is a method where we find the value of a single unit from the value of multiple units and the value of multiple units from the value of a single unit.
Steps to Use Unitary Method
First, let us make a note of the information we have. There are 5 ice-creams. 5 ice-creams cost $125.
Step 1: Let’s find the cost of 1 ice cream. In order to do that, divide the total cost of ice-creams by the total number of ice-creams. The cost of 1 ice-cream = Total cost of ice-creams/Total number of ice-creams = 125/5 = 25. Therefore, the cost of 1 ice cream is $25.
Step 2: To find the cost of 3 ice-creams, multiply the cost of 1 ice cream by the number of ice-creams. The cost of 3 ice-creams is cost of 1 ice-cream × number of ice-creams = 25 × 3 = $75. Finally, we have the cost of 3 ice-creams i.e. $75.
Given:
Total number of classes = 9
Number of student in each class = 25
Number of teacher = 4
Number of chaperones = Double of teacher
Bus hold = 45 people
Now,
Total number of student = 9 × 25
= 225
Number of chaperones = 4 × 2
= 8
Total people = 225 + 8 + 4
= 237
Least number of bus require for trip = Total people / Bus hold
= 237 / 45
= 5.266
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If the initial amount of iodine-131 is 537 grams , how much is left after 10 days?
Answer:
225.78 grams
Step-by-step explanation:
To solve this question, we would be using the formula
P(t) = Po × 2^t/n
Where P(t) = Remaining amount after r hours
Po = Initial amount
t = Time
In the question,
Where P(t) = Remaining amount after r hours = unknown
Po = Initial amount = 537
t = Time = 10 days
P(t) = 537 × 2^(10/)
P(t) = 225.78 grams
Therefore, the amount of iodine-131 left after 10 days = 225.78 grams
LCM of x<sup>2</sup>+5x+6 and x<sup>2</sup>-x-6 is ………………………
Answer:
[tex] (x^2 - 9)(x + 2) [/tex]
Step-by-step explanation:
Given:
[tex] x^2 + 5x + 6 [/tex]
[tex] x^2 - x - 6 [/tex]
Required:
LCM of the polynomials
SOLUTION:
Step 1: Factorise each polynomial
[tex] x^2 + 5x + 6 [/tex]
[tex] x^2 + 3x + 2x + 6 [/tex]
[tex] (x^2 + 3x) + (2x + 6) [/tex]
[tex] x(x + 3) + 2(x + 3) [/tex]
[tex] (x + 2)(x + 3) [/tex]
[tex] x^2 - x - 6 [/tex]
[tex] x^2 - 3x +2x - 6 [/tex]
[tex] x(x - 3) + 2(x - 3) [/tex]
[tex] (x + 2)(x - 3) [/tex]
Step 2: find the product of each factor that is common in both polynomials.
We have the following,
[tex] x^2 + 5x + 6 = (x + 2)(x + 3) [/tex]
[tex] x^2 - x - 6 = (x + 2)(x - 3) [/tex]
The common factors would be: =>
[tex] (x + 2) [/tex] (this is common in both polynomials, so we would take just one of them as a factor.
[tex] (x + 3) [/tex] and,
[tex] (x - 3) [/tex]
Their product = [tex] (x - 3)(x + 3)(x +2) = (x^2 - 9)(x + 2) [/tex]
The cost of milk is modeled by a linear equation where four quarts (one gallon) costs $3.09 while two quarts
(half-gallon) costs $1.65. Write the linear equation that expresses the price in terms of quarts. How much would
an eight-quart container of milk cost?
Answer:
linear equation to express the price is:
y=0.72x+0.21
An eight quarts will cost : $5.97
Step-by-step explanation:
linear equation represent y=mx+b
let x=quarts ( x=4, x=2)
y= price (3.09 and y=1.65 )
two points (4,3.09) and (2,1.65)
need to find the slope m:
y2-y1/x2-x1
(1.65-3.09)/(2-4) ⇒ m=0.72
y=0.72x+b find b at point (2,1.65)
1.65=0.72(2) +b ⇒ b=0.21
y=0.72x +0.21
check : point (4,3.09)
y=0.72(4) +0.21
y=3.09 ( correct)
An eight quarts will cost :
y=0.72(8)+0.21
y=5.97 dollars
|3x–1|=8 please help!!!!!
Answer: -3
Add 1 to both sides
[tex]3x-1+1=8+1[/tex]
[tex]3x=9[/tex]
Divide both sides by 3
[tex]3x/3=9/3\\x=3[/tex]
Type the correct answer in the box. Use numerals instead of words. If necessary, use / for the fraction bar. Stacy goes to the county fair with her friends. The total cost of ride tickets is given by the equation c = 3.5t, where c is the total cost of tickets and t is the number of tickets. If Stacy bought 15 tickets, she would spend $
Answer:
$52.2Step-by-step explanation:
Given her total cost of ride tickets modeled by the equation c = 3.5t where c is the total cost of tickets and t is the number of tickets, If Stacy bought 15 tickets, to know the amount she would spend on 15 tickets, we will substitute t = 15 into the modeled equation as shown;
[tex]c = 3.5t\\when t = 15\\\\c = 3.5(15)\\\\c = \frac{35}{10} * 15\\ \\c = \frac{5*7}{5*2} * 15\\\\[/tex]
[tex]c = \frac{7}{2} * 15\\ \\c = \frac{105}{2}\\ \\c = \ 52.2[/tex]
Hence Stacy would spend $52.2 on 15 tickets
Answer:
I hope this helps!
Step-by-step explanation:
Please solve (will make brainiest)
Answer:
1a) 1/64
1b) 1/169
1c) 1/9
Step-by-step explanation:
You have to apply Indices Law :
[tex] {a}^{ - n} = \frac{1}{ {a}^{n} } [/tex]
Question A,
[tex] {4}^{ - 3} = \frac{1}{ {4}^{3} } = \frac{1}{64} [/tex]
Question B,
[tex] {13}^{ - 2} = \frac{1}{ {13}^{2} } = \frac{1}{169} [/tex]
Question C,
[tex] {( - 3)}^{ - 2} = {( - \frac{1}{3}) }^{2} = \frac{1}{9} [/tex]
I NEED YOUR HELP PLS
Answer:
For question 1 you can try dividing each of the value
For instance, you can divide 9 by 25 and see if you get a nice number
e.g. 1/8=0.125, numbers like these
For the second question, you can find the fraction by dividing 1000 starting with the decimal points
e.g 0.650, you would be plotting 650/1000 and you would simplify the fraction to the lowest value any value above the decimal point you can multiply by the denominator and add the nominator value to get your final answer.
Step-by-step explanation:
Answer:
Write the denominator in its prime factors. If the prime factorization of the denominator of a fraction has only factors of 2 and factors of 5, the decimal expression terminates. If there is any prime factor in the denominator other than 2 or 5, then the decimal expression repeats.
example: 9/25
25 = 5*5, so it will be terminating
example: 7/12
12 = 3*2*2, which contains a 3, so it will be repeating.
pls help with sum geometry
YES! quite easily.
I hope you can see the two pairs of corresponding angles between the parallel lines. they'll be equal
and then there's a pair of vertically opposite angle at centre.
that means all pairs of corresponding angles are equal, thus, triangles are similar by AAA
Answer:
[tex]\Large \boxed{\mathrm{D}}[/tex]
Step-by-step explanation:
The triangles can be proven by AA or Angle-Angle similarity.
[tex]\angle QUR \cong \angle TUS[/tex]
The vertical angles are congruent.
[tex]\angle R \cong \angle S[/tex]
The alternate interior angles are congruent.
Two buildings are 12m apart on the same horizontal level. From the top of the taller building, the angle of depression of the bottom of the shorter building is 48degrees and from the bottom, the angle of of elevation of the top of the shorter building is 36 degrees. Calculate the difference in the heights of the buildings
Answer:
4.61 m
Step-by-step explanation:
The angle of depression of the bottom of the shorter building from the top of the taller building = 48° equals the angle of elevation of the top of the taller building from the bottom of the shorter building
Using trig ratios
tan48° = H/d where H = height of taller building and d = their distance apart = 12 m
H = dtan48° = 12tan48° = 13.33 m
Also, the angle of elevation of the top of the shorter building from the bottom of the taller building is 36°
Using trig ratios
tan36° = h/d where h = height of shorter building
h =dtan36° = 12tan36° = 8.72 m
Now, the difference in height of the buildings is thus H - h = 13.33 m - 8.72 m = 4.61 m
Find the value of x. Round to the nearest tenth.Find the value of x. Round to the nearest tenth.
Answer:
x = 55.6Step-by-step explanation:
In order to find the value of x we use sine
sin ∅ = opposite / hypotenuse
From the question
x is the hypotenuse
the opposite is 19
So we have
sin 20 = 19/x
x = 19/sin 20
x = 55.55
We have the final answer as
x = 55.6 to the nearest tenthHope this helps you
Answer:
x = 55.6
Step-by-step explanation:
I answered all my work correctly but I don’t understand this one.
1: The best statement for reason 6 of this proof is -∠A ≅ ∠C
-∠B ≅ ∠D
-∠B and ∠D are supplements
-∠B ≅ ∠B
2.The best reason for statements 3.5. and 7 in this proof is
- Alternate interior angles are congruent.
-Corresponding angles are congruent.
-Alternate exterior angles are congruent.
-Interior angles on the same sides of a transversal are supplements.
3. The best statement for reason 8 of this proof is
-∠B ≅ ∠B -∠A and ∠C are supplements.
-∠B ≅ ∠D
-∠A ≅ ∠C
Answer:
1) -∠B ≅ ∠D
2) -Interior angles on the same side of a transversal are supplementary
3) -∠A ≅ ∠C
Step-by-step explanation:
1) Given that ∠A and ∠B are supplements and ∠A and ∠D are supplements, we have; ∠B ≅ ∠D
2) Given that ABCD is a parallelogram, therefore ∠A and ∠B, ∠A and ∠D and ∠B and ∠C are interior angles on the same side of a transversal and are therefore supplementary
3) Given that ∠A and ∠B and ∠B and ∠C are supplementary, therefore, ∠A ≅ ∠C.
What is 12.5% of 72
Answer:
[tex]\boxed{9}[/tex]
Step-by-step explanation:
[tex]\sf of \ refers \ to \ multiplication.[/tex]
[tex]12.5\% \times 72[/tex]
[tex]\frac{12.5}{100} \times 72[/tex]
[tex]\sf Multiply.[/tex]
[tex]\frac{900}{100} =9[/tex]
4x
5.
If 7:5 = (x + 2y): (x - y), find the value of
5y
Answer:
5/2 OR 2.5
Step-by-step explanation:
( x + 2y ) = 7 , ( x - 2y ) = 5
x = 7 - 2y , x = 5 + 2y
substitute the two eqns together:
7 - 2y = 5 + 2y
7 - 5 = 2y + 2y
2 = 4y
y = 1/2
when y = 1/2 ,
5y = 5(1/2)
= 5/2 OR 2.5
Which polynomial is a factor of both expressions? x – 8 x + 7 x – 2 (x – 2)2
Answer:
C. x-2
Step-by-step explanation:
edge
Answer: the 3rd the answer c
x-2
Step-by-step explanation:
What’s is the greatest common factor of 100x^2 - 250xy + 75x
Answer:
The greatest common factor of the expression is 25x
Step-by-step explanation:
Here, we are interested in giving the greatest common factor of the expression.
We can do this by factorization till we have no common factors left.
the expression is;
100x^2 -250xy + 75x
we start with the common factor x;
x(100x -250y + 75)
The next thing to do here is to find the greatest common factor of 100,250 and 75.
The greatest common factor here is 25.
Thus, we have;
25x(4x -10y + 3)
There is no more factor to get from the terms in the bracket. This simply means that the terms in the bracket are no longer factorizable
So the greatest common factor we have is 25x
1.Solve by factorization method: x+1/x=11 1/11 2.Comment on the nature of roots for 4x^2-5=2(〖x+1)〗^2-7 plz, help...
Answer:
The equation
[tex]4\,x^2-5=2\,(x+1)^2-7[/tex]
can be solved by first expanding all indicated operations, and later when the constant terms disappear, by factoring out 2x , leaving the equation as a product of two factors equal zero, from which it is easy to extract the roots. See below.
Step-by-step explanation:
When solving for x in the following expression, and using factoring to apply at the end the zero product theorem:
[tex]4\,x^2-5=2\,(x+1)^2-7\\4\,x^2-5=2\,(x^2+2x+1)-7\\4\,x^2-5=2\,x^2+4\,x+2-7\\4\,x^2-5=2\.x^2+4\,x-5\\4\,x^2=2\,x^2+4\,x\\4\,x^2-2\,x^2-4\,x=0\\2\,x^2-4\,x=0\\2\,x\,(x-2)=0[/tex]
We observe that for the last product, to get a zero, x has to be zero (making the first factor zero), or x has to be "2" making the binomial factor zero.
The width of a rectangle measures (6.8d-4.2)(6.8d−4.2) centimeters, and its length measures (9.2d+8.7)(9.2d+8.7) centimeters. Which expression represents the perimeter, in centimeters, of the rectangle?
Answer:
The perimeter of the rectangle is represented by [tex]p = 32\cdot d + 9[/tex], measured in centimeters.
Step-by-step explanation:
The perimeter ([tex]p[/tex]) of a rectangle, measured in centimeters, is represented by this formula:
[tex]p = 2\cdot (w+l)[/tex]
Where [tex]w[/tex] and [tex]l[/tex] are width and length, measured in centimeters.
If [tex]w = 6.8\cdot d-4.2[/tex] and [tex]l = 9.2\cdot d+8.7[/tex], the expression that represents the perimeter is:
[tex]p = 2\cdot (16\cdot d +4.5)[/tex]
[tex]p = 32\cdot d + 9[/tex]
The perimeter of the rectangle is represented by [tex]p = 32\cdot d + 9[/tex], measured in centimeters.
Suppose that $9500 is placed in an account that pays 9% interest compounded each year.
Assume that no withdrawals are made from the account.
Follow the instructions below. Do not do any rounding.
(a) Find the amount in the account at the end of 1 year.
so
(b) Find the amount in the account at the end of 2 years.
$
?
Answer:
$11286.95 second year
$10335 first year
Step-by-step explanation:
9% of 9500 is 855, 9500 plus 855 = 10335. (first year)
9% of 10335 is 931.95, and 10335+931.95 is 11286.95. (second year)
The amount in the account at the end of 1 year $10335 (first year)
The amount in the account at the end of 2 years $11286.95.
What is the compound interest?Compound interest is when you earn interest on both the money you've saved and the interest you earn.
Formula:
A = P(1 + {r}/{n})^{n.t}
here, we have,
$9500 is placed in an account that pays 9% interest compounded each year.
so, we get,
9% of 9500 is 855,
9500 plus 855 = 10335. (first year)
again,
9% of 10335 is 931.95,
and 10335+931.95 is 11286.95. (second year)
Hence, The amount in the account at the end of 1 year $10335 (first year)
The amount in the account at the end of 2 years $11286.95.
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4.
Aliyah, Brenda and Candy share a sum of money in the ratio of 3:5:6. After
Candy gives $100 to Aliyah and $50 to Brenda, the ratio becomes 2 : 3:3.
(a) Suppose Aliyah has $3x at the start, express Candy's initial sum of money in
terms of x.
(b) Find the value of x.
(c) Hence, how much money does Brenda have in the end?
Answer:
(a) Candy's initial sum as a terms of x is $6x
(b) x = $60
(c) $350
Step-by-step explanation:
The given parameters are;
The ratio in which Aliyah, Brenda and Candy share the sum of money = 3:5:6
The amount Candy later gives Aliyah = $100
The amount Candy later gives Brenda = $50
The new ratio of the sum of the shared money between Aliyah, Brenda and Candy = 2:3:3
(a) Whereby Aliyah has $3x at the start, we have;
Total sum of mony = Y
Amount of Aliyah's initial share = Y × 3/(3 + 5 + 6) = Y×3/14
Therefore, Y×3/14 = $3x
x = Y×3/14 ÷ 3 = Y/14
Amount of Candy's initial share = Y × 6/14
Therefore Candy's initial sum as a terms of x = $6x
(b) Given that Aliyah's and Candy's initial sum as a function of x are $3x and $6x, therefore, in the ratio 3:5:6, Brenda's initial sum as a function of x = $5x
Which gives;
Total amount of money = $14x
With
6x - 150, 3x + 100, and 5x + 50, the ratio =is 2:3:3
Therefore, we have;
14·x × 2/(2 + 3 + 3) = (6·x - 150)
14·x × 2/(8) = (6·x - 150)
14·x × 1/4 = (6·x - 150)
7·x/2 = (6·x - 150)
12·x - 300 = 7·x
12·x - 7·x = 300
5·x = 300
x = $60
(b) The final amount of money with Brenda = 5x + 50 = 5 × 60 + 50 = $350
The final amount of money with Brenda = $350.
find the multiplicative inverse of 3 by 4 minus 5 by 7
Answer:
28
Step-by-step explanation:
[tex]\frac{3}{4}-\frac{5}{7}[/tex]
Least Common Denominator of 4 & 7 is 4 * 7 = 28
[tex]\frac{3}{4}-\frac{5}{7}=\frac{3*7}{4*7}-\frac{5*4}{7*4}\\\\\\=\frac{21}{28}-\frac{20}{28}\\\\\\=\frac{21-20}{28}\\\\\\=\frac{1}{28}[/tex]
Multiplicative inverse of [tex]\frac{1}{28}[/tex] is [tex]\frac{28}{1} = 28[/tex]
. Find two polynomial expressions whose quotient, when simplified, is 1/x . Use that division problem to determine whether polynomials are closed under division.
Answer:
The two polynomials are:
(x + 1) and (x² + x)
Step-by-step explanation:
A polynomial is simply an expression which consists of variables & coefficients involving only the operations of addition, subtraction, multiplication, and non - negative integer exponents of variables.
Now, 1 and x are both polynomials. Thus; 1/x is already a quotient of a polynomial.
Now, to get two polynomial expressions whose quotient, when simplified, is 1/x, we will just multiply the numerator and denominator by the same polynomial to get more quotients.
So,
Let's multiply both numerator and denominator by (x + 1) to get;
(x + 1)/(x(x + 1))
This gives; (x + 1)/(x² + x)
Now, 1 and x are both polynomials but the expression "1/x" is not a polynomial but a quotient and thus polynomials are not closed under division.
5. Find the product of p(x) and q(x) if p(x) = 2x+7 and q(x) = 4x-9
a. Is p(x) a polynomial? If not, give an explanation.
b. Is q(x) a polynomiala If not, give an explanation.
c. Is the product a polynomials If not, give an explanation,
d. If the product is a polynomial, identify type and degree.
Answer:
p(x), q(x), and their product are all polynomials.
p(x) · q(x) = 6x² + 10x - 63
Step-by-step explanation:
First of all P(x) and q(x) are polynomials because polynomials refer to any sum, difference, or product of a collection of algebraic terms. The word polynomials is general. P(x) and q(x) are polynomials but more specifically they are binomials since they only have two terms. Their product is a polynomial as well, but more specifically its a trinomial because it has three terms.
process of multiplying
Using the distributive property (or foil method) when multiplying p(x) and q(x) you would first get the expression 6x² - 18x + 28x - 63. From here you would combine "like terms". This would give you your final answer of
6x² + 10x - 63. Sorry, I couldn't help you with the D question but I hope this helps ;)
Can someone please tell me how to solve this problem??!! I literally have to go back in math if I don’t pass this HELP!!
Answer:
D. 270° < φ < 360°Step-by-step explanation:
Imagine coordinate system
I quarter is where x>0 and y>0 {right top} and it is (0°,90°)
II quarter is where x<0 and y>0 {left top} and it is (90°,180°)
III quarter is where x<0 and y<0 {left bottom} and it is (180°,270°)
IV quarter is where x>0 and y<0 {right bottom} and it is (270°,360°)
Now, we have an angle wich vertex is point (0,0) and one of its sides is X-axis and the second lay at one of the quarters.
For the trig functons of an angle created by this second side always are true:
In first quarter all functions are >0
in second one only sine
in third one: tangent and cotangent
and in fourth one: cosine
{You can check this by selecting any point on the second side of angle and put it's coordinates to formulas of these functions:
[tex]\sin \phi=\dfrac y{\sqrt{x^2+y^2}}\,,\quad \cos \phi=\dfrac x{\sqrt{x^2+y^2}}\,,\quad \tan\phi=\dfrac yx\,,\quad \cot\phi=\dfrac xy[/tex] }
So:
sinφ<0 ⇒ III or IV quarter
tanφ<0 ⇒ I or IV quarter
IV quarter ⇒ φ ∈ (270°, 360°)