Answer:
Volume is 
Solution:
As per the question:
Diameter, d = 40 m
Radius, r = 20 m
Now,
From north to south, we consider this vertical distance as 'y' and height, h varies linearly as a function of y:
iff
h(y) = cy + d
Then
when y = 1 m
h(- 20) = 1 m
1 = c.(- 20) + d = - 20c + d (1)
when y = 9 m
h(20) = 9 m
9 = c.20 + d = 20c + d (2)
Adding eqn (1) and (2)
d = 5 m
Using d = 5 in eqn (2), we get:

Therefore,

Now, the Volume of the pool is given by:

where
A = 

Thus




![V = [- 533.33cos\theta + 1000\theta]_{0}^{2\pi}](https://tex.z-dn.net/?f=V%20%3D%20%5B-%20533.33cos%5Ctheta%20%2B%201000%5Ctheta%5D_%7B0%7D%5E%7B2%5Cpi%7D)

4(r)^x=y
4(r)^(1)=2
r=1/2
y=4*(1/2)^x
Answer:

Step-by-step explanation:
Given that:

for 
That means, angle
is in the 3rd quadrant.
To find:
Value of cot(t)
Solution:
First of all, let us recall what trigonometric ratios are positive and what trigonometric ratios are negative in 3rd quadrant.
In 3rd quadrant, tangent and cotangent are positive.
All other trigonometric ratios are negative.
Let us have a look at the following identity:

here, 
So, 

But, angle
is in 3rd quadrant, so value of

<h3>
Answer: 15 hours (choice D)</h3>
================================================
Work Shown:
(6 hours)/(8 trees) = (x hours)/(20 trees)
6/8 = x/20
6*20 = 8*x ... cross multiply
120 = 8x
8x = 120
x = 120/8
x = 15
It takes him 15 hours to plant 20 trees.