Evaluate by using a substitution prior to integration by parts. Thanks for any help!
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Try u = ln(t). Then t = exp(u). du = dt/t so dt = exp(u)du. Now you've got an integral with cos(u)exp(u)du. Remember cos(u) = {exp(iu)+exp(-iu)}/2 ? Now it's all exponentials.
and Take your u equation and solve for t now. Solve and then back substitute
Use the substitution u=ln(t) and then use the formula which you can calculate yourself, instead of memorizing. (I personally prefer the former because you don't need it that much.)
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