Integral problem?
Integral of (sinx)/(sinx+tanx)
here is someone's answer
sinx / (sinx + tanx)
multiply throughout by cotx = cosx / sinx to get
cosx / (cosx + 1)
= [2cos^2 (x/2) - 1 ] / [2cos^2 (x/2) ]
= 1 - 1 / 2cos^2 (x/2)
= 1 - 1/2 * sec^2 (x/2)
I don't get where is the x/2 came from
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Verified answer
cosx / (cosx + 1)
cos( 2A) =2cos^2 (A) -1
so cos (x) =2cos^2(x/2) - 1
you use this result when you have an expression involving a cos term +1. This gets rid of the +1.