Integration By Substitution watch

1. Hi Everyone,

I've just been going over this question:

Find the integral of cosh(u)/(1+sinh^2(u))

Now i got the correct answer + tan^-1(sinh(u))

But a step in the process has me confused.

When you substitute x=sinh(u) at the start, the cosh(u)'s cancel and your left with the intergral of 1/(1+x^2) dx could you not just integrate this to get (1/(2x))*(ln(1+x^2)) + C as the derivative of 1/(2x))*(ln(1+x^2)) + C would be 1/(1+x^2) right? or am i just making a silly mistake somewhere?

Cheers
2. Oops, forget all that (can you not delete threads these days)...

Realised the derivative of 1/(2x))*(ln(1+x^2)) is no where near that...

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