Question

integrate sqrt(1+4*r^2)*rdr
It's in a double integral converted to polar coordinates. How do I multiply the r and integrate?

Answer 1

That has a standard antiderivative. If it helps, you can make a substitution:
u = 1+4r^2
du = 8r dr

Answer 2

You're the best!!!!!! I've never used this before, but it's great. Thanks!!!