difficult integration

ookt2c

integrate sin^4(2x) without using the reduction formula.im stuck.
im pretty sure you have to use integration by parts.

Big-T

Try using double-angle formulae a couple of times.

rock.freak667

The double angle formula for cos will help I believe.

mrandersdk

don't know what the reduction formula is, maybe it is the trick i'm about to give you

[tex] \int sin(2x)^4 dx = \frac{1}{2} \int sin(u)^4 du = \frac{1}{2} \int (sin(u)^2)^{3/2} sin(u) du = \frac{1}{2} \int (1-cos(u)^2)^{3/2} sin(u)du = \frac{1}{2} \int (1-t^2)^{3/2} dt = \int sqrt((1-t^2)^3) [/tex]

maybe you can do this???, of cause you have to keep track of all the substitutions to get how sin and y are related but that should be possible.

sutupidmath

This thread is already somewhere else. I mean the exact same question.

http://www.physicsforums.com/showthread.php?t=213617