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Ira Lisetskai [31]
3 years ago
15

Why dA = r dr d(theta)?

Mathematics
1 answer:
Serjik [45]3 years ago
8 0
For dA in  a circle, the r  value varies ,  but its area is still rdrd(theta) but r (and theta) differs depending where the region is
and the regions could be any regions as long as it is a continuous region

hope this helps
 
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What is this: 4810 ÷ 13?
natali 33 [55]

Answer:

370

Step-by-step explanation:

6 0
2 years ago
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Help please and explain why
andrew-mc [135]

Answer:

9 cm tall

Step-by-step explanation:

The formula to find the volume of a cylinder is

V = pi r^2 (h)

pi r^2 is the base

Plug in the volume and the base

198 = 22 (h)

divide by 22

9 = h

7 0
3 years ago
Suppose that scores on a knowledge test are normally distributed with a mean of 60 and a standard deviation of 4.3. Scores on an
Sphinxa [80]

Question:

(c) Boris also took a logic test. His z-score on that test was +0.93 . Does this change the answer to which test Boris performed better on? Explain your answer using z-scores.

Answer:

The answers to the questions are;

(a) Based on the z score, Boris perform better on his aptitude test.

(b) Based on the z score, Callie perform better on his knowledge test .

(c) For Boris since +0.93 = z_{logic} >  z_{knowledge}  >  z_{aptitude}

Yes as Boris now performed best on the logic test.

Step-by-step explanation:

The z-score of a score is a measurement of the score withe respect to its distance from the mean as a factor of the standard deviation.

To solve the question, we note that we are required to find the z score as follows.

z score is given by z = \frac{x -\mu}{\sigma}

Where:

z = Standard score

x = Score

σ = Standard deviation

μ = Mean

(a) To find out which test did Boris performed better usin z score, we have

Boris scored a

57 on the knowledge test and

106 on the aptitude test

Therefore the z sore for the knowledge test is

z = \frac{x -\mu}{\sigma}

Here

x = 57

μ = 60

σ = 4.3

Therefore

z_{knowledge} = \frac{57 -60}{4.3} = -3/4.3 = -30/43 = -0.6977

The z sore for Boris on the aptitude test is

Here

x = 106

μ = 110

σ = 7.1

z_{aptitude} = \frac{106 -110}{7.1} = -40/17 = -0.5634

Based on the z score, Boris perform better on the aptitude test as his z score is higher (on the number line), --0.5634, compared to the z score on the knowledge test , -0.6977

(b) For Callie we have

Callie scored a

63 on the knowledge test and

114 on the aptitude test

Therefore the z sore for the knowledge test is

z = \frac{x -\mu}{\sigma}

Here

x = 63

μ = 60

σ = 4.3

Therefore

z_{knowledge} = \frac{63 -60}{4.3} = 3/4.3 = 30/43 = 0.6977

The z sore for Callie on the aptitude test is

Here

x = 114

μ = 110

σ = 7.1

z_{aptitude} = \frac{114 -110}{7.1} = 40/17 = 0.5634

Based on the z score, Callie perform better on the knowledge test as his z score is higher (on the number line), 0.6977, compared to the z score on the aptitude test , 0.5634.  

(c) If z_{logic}  = +0.93 then sinc for Boris z_{knowledge} = -0.6977 and

z_{aptitude}=  - 0.5634 then

z_{logic} >  z_{knowledge}  >  z_{aptitude}

Therefore Boris now performed best on the logic test.

6 0
3 years ago
Find all the zeros of the polynomial function p(x) = x3 – 5x2 + 33x – 29
hram777 [196]

Answer:

\large \boxed{\sf \ \ x=1, \ \ x=2+5i, \ \ x=2-5i \ \ }

Step-by-step explanation:

Hello,

I assume that we are working in \mathbb{C}, otherwise there is only one zero which is 1. Please consider the following.

First of all, <u>we can notice that 1 is a trivial solution</u> as

   p(1) = 1^3-5\cdot 1^2 + 33\cdot 1-29=1-5+33-29=0

It means that (x-1) is a factor of p(x) so we can find two real numbers, a and b, so that we can write the following.

p(x)=(x-1)(x^2+ax+b)=x^3+ax^2+bx-x^2-ax-b=x^3+(a-1)x^2+(b-a)x-b

Let's identify like terms as below.

a-1 = -5 <=> a = -5 + 1 = -4

b-a = 33

-b = -29 <=> b = 29

So

\boxed{ \ p(x)=(x-1)(x^2-4x+29) \ }

Now, we need to find the zeroes of the second factor, meaning finding x so that:

x^2-4x+29=0 \ \text{ complete the square, 29 = 25 + 4}  \\ \\  x^2-2\cdot 2 \cdot x+2^2+25=0 \\ \\ (x-2)^2=-25=(5i)^2 \ \text{ take the root } \\ \\x-2=\pm 5i \ \text{ add 2 } \\ \\  x = 2+5i \ \text{ or } \ x = 2-5i

Hope this helps.

Do not hesitate if you need further explanation.

Thank you

5 0
3 years ago
If f(x) = 2x - 6 and g(x) = 3x + 9, find (f+g)(x)
valina [46]

Answer:

(f+g)(x)  =  5x + 3

Step-by-step explanation:

f(x) = 2x - 6 and g(x) = 3x + 9, find (f+g)(x)

(f+g)(x) = f  + g  =  (2x - 6)  + (3x + 9) =   5x + 3

(f+g)(x) = f  + g  =  5x + 3

3 0
3 years ago
Read 2 more answers
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