Thread: Relate Rates Problem

Here is the question I am having trouble with:
The sun is passing over a 100 m tall building. The angle θ made by the sun with the ground is increasing at a rate of pi/20 rads/min. At what rate is the length of the shadow of the building changing when the shadow is 60 m long? Give your answer in exact values.
So far I have got:
100cosfata=x

dx/dt=-100(cosfata)(dfata/dx)
Dont no where to get cosfata from.

"Increasing at a rate of rads/min?"

How many radians per minute?

Oh my gosh I have read this problem so many times I can just picture the numbers when they are not even there. Ugh.
It is pi/20 rads/min

The sun is passing over a 100 m tall building. The angle θ made by the sun with the ground is increasing at a rate of pi/20 rads/min. At what rate is the length of the shadow of the building changing when the shadow is 60 m long?

But how do I find a value for -csc^2fata

Originally Posted by mjo

But how do I find a value for -csc^2fata

review your basic right triangle trig ...



square the result and change its sign to get the value of




btw ... is prounounced "theta" , not "fata"

I found my original problem. Thanks guys