The base of an isosceles triangle is 10 feet long and the base angles are decreasing at a rate of 2° per second. Find the rate of change of the area when the base angles are 45°.

Answer 1

we have the height h is

h = 5tanθ

a = 5h = 25tanθ
da/dt = 25sec^2θ dθ/dt

Now just plug in your numbers (in radians!)

Answer 2

Thank you Sir ☺

Answer 3

But where did the a=5h come from?

Answer 4

did you actually draw an isosceles triangle with a base of 10?

A = 1/2 bh

Let's not forget the basics now that we're in calculus!

Answer 5

Oh yes. Sorry sir. i just got confused. Thank you :)