Homework Help: calculus

Posted by Anonymous on Sunday, November 18, 2007 at 12:43am.

The radius of a circle is increasing at a nonzero rate, and at a certain instant, the rate of increase in the area of the circle is numerically equal to the increase in its circumstance. At this instant, the radius of the cirle is...

Here is what I did: (unsure)
pi(r^2)=2pi(r)
r^2-r=0
r(r-2)=0
r=2

calculus - Reiny, Sunday, November 18, 2007 at 1:20am
no, it is the rates of increase that are equal, so you have to set the derivatives equal.

dA/dr = 2pi(r)
dC/dr = 2pi

so 2pi(r) = 2 pi
r = 1

Answer this Question

Related Questions

Calculus - Let V be the volume of a right circular cone having height h and ...
calculus - 3. The radius r of a sphere is increasing at a constant rate of 0.04 ...
college calculus - 1) each side of a square is increasing at a rate of 6cm/s. At...
Calculus AB - The volume V or a cone (V = 1/3 π r² h) is ...
calculus - At the instant when the radius of a cone is 3 inches, the volume of ...
AP calculus AB - At the instant when the radius of a cone is 3 inches, the ...
Calculus - A spherical balloon is inflated at a rate of 10 cubic feet per minute...
calculus help please - At the instant when the radius of a cone is 3 inches, the...
calculus - at a certain instant the base of a triangle is 5 inches and is ...
math - Resolved QuestionShow me another » AP Calculus related rates ...

For Further Reading

First Name:
School Subject:
Answer: