- #1

yecko

Gold Member

- 277

- 8

## Homework Statement

## Homework Equations

in the pic

## The Attempt at a Solution

why is there an extra "r" in the highlighted line?

my attempt:

## \int_0^{2\pi}\int_0^2\int_{r^2}^41\ dy\ r\ dr\ d\theta ##

= ##\int_0^{2\pi}\int_0^2\left(4-r^2\right)\ r\ dr\ d\theta##

thanks