How do I evaluate this indefinite integral?

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
4 replies · 2K views
zorro
Messages
1,378
Reaction score
0

Homework Statement



How do I evaluate this?

gif.latex?\int\frac{cos7x-cos8x}{1+2cos^2x}dx.gif


A hint will do.
 

Attachments

  • gif.latex?\int\frac{cos7x-cos8x}{1+2cos^2x}dx.gif
    gif.latex?\int\frac{cos7x-cos8x}{1+2cos^2x}dx.gif
    942 bytes · Views: 445
Physics news on Phys.org
Abdul Quadeer said:

Homework Statement



How do I evaluate this?

gif.latex?\int\frac{cos7x-cos8x}{1+2cos^2x}dx.gif


A hint will do.

Convert the expression using trig identities and then try by-parts integration or substitution.
 
Yeah, looking at the answer, It looks like a few trig identities (particularly the denominator), and then integration by parts (many times). Be warned, the answer is rather ugly (many lines ugly...)

by any chance did this come up in a Fourier decomposition (I am looking at the graph of it)? :P
 
n1person said:
Yeah, looking at the answer, It looks like a few trig identities (particularly the denominator), and then integration by parts (many times). Be warned, the answer is rather ugly (many lines ugly...)

by any chance did this come up in a Fourier decomposition (I am looking at the graph of it)? :P

Looking at the answer? Where is it?
No it is not from Fourier decomposition.