Question

A square is inscribed in a circle. If the radius of the circle is increasing at a rate of 3 cm/min, find how fast the area of the square is increasing when the radius is 10 cm.

Answer 1

OK, here goes:

Answer 2

r=d/2
s=d/sqrt(2)
a=s^2=2r^2
da/dr = 4r
da/dt = da/dr dr/dt = 4r dr/dt = 4r (3 cm/min) = 12r cm/min
at r=10cm this is
da/dt = 120 cm^2/min

Answer 3

thank you =)

Answer 4

You're welcome. Good problem. Points for your math teacher.