Hello,

I fixed the latex. should be { } not ( )

have you tried substituting ?

so we have

and

which will give a partial decomposition...

so let's try

so we have

much better ! can you finish it ?

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okay, you changed the problem... however, it doesn't change the method. the best substitution seems to be u=cos(x)

as for the boundaries, i'll leave it to you =)