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Difficult integration 
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#1
Feb608, 05:38 PM

P: 16

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


#2
Feb608, 06:05 PM

P: 64

Try using doubleangle formulae a couple of times.



#3
Feb608, 06:09 PM

HW Helper
P: 6,206

The double angle formula for cos will help I believe.



#4
Feb708, 03:53 AM

P: 230

Difficult integration
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 (1cos(u)^2)^{3/2} sin(u)du = \frac{1}{2} \int (1t^2)^{3/2} dt = \int sqrt((1t^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. 


#5
Feb708, 10:38 AM

P: 1,635

This thread is already somewhere else. I mean the exact same question.
http://www.physicsforums.com/showthread.php?t=213617 


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