tough integration problem

[mathrocks]

Does anyone know how to integrate cos(sqrt x) ?? I know the answer, i need to know the steps to do it?

Thanks

[HallsofIvy]

Let u= \sqrt{x}= x^{\frac{1}{2}}. Then du= \frac{1}{2}x^{-\frac{1}{2}}dx so that dx= 2x^{\frac{1}{2}}du= 2udu.

\int{cos(\sqrt{x})dx}= \int{2u cos(u)du}.

Now use integration by parts.

[Dr Transport]

let \sqrt{x} = y be the variable substution and integrate by parts.

[Dr Transport]

as I was typing, HallsofIvy gopt it down first.....