## anonymous 4 years ago The area A of a circle is a function with respect to its radius r: A = pi r^2. (dA)/(dr) =

dA=2pi*r

2. anonymous

that's the equation so I just need to plug in the numbers, right?

you don't have to plug in anything if this is the complete text

4. anonymous

what is the star between pi and r represent?

5. TuringTest

times

6. anonymous

Remember that pi is just a number and the radius, r, is your independent variable. So you take the derivative using the power rule. So, A'= 2*(pi)r^(2-1), or just 2(pi)r.

7. TuringTest

$A=\pi r^2$$\frac{dA}{dt}=\frac d{dt}(\pi r^2)=\pi\frac d{dt}r^2=\pi(2r)=2\pi r$

8. TuringTest

right, power rule

9. anonymous

that what I got ok thanks