Question

Evaluate the integral.
x sin 3x dx from 0 to 1

Answer 1

No. It's x sin (3x) dx

Answer 2

sub u=3x

Answer 3

I'm pretty sure this can be solved by integration by parts

where,
f(x) = x
g'(x) = sin(3x)

watch this video

https://www.youtube.com/watch?v=dqaDSlYdRcs

maybe it can explain it bus basically

\[\int\limits_{}^{}g'(x)f(x)dx = g(x)f(x) - \int\limits_{}^{}f'(x)g(x)dx\]