Question

For a circle with area \[A=\pi r^2\], what is \[\frac{dA}{dr}\]?

Options

• \[2\pi r\]

• \[2\pi r^2\]

• \[\pi r^2\]

• \[\pi r\]

Answer 1

Differentiate \[A=\pi r^2\] with respect to \(r\).
The derivative is \[\frac{dA}{dr}=2\pi r\], the rate of change of area with respect to radius.