# Integration of Trigonomic Functions

1. Oct 4, 2011

### Andyb43

I have come across the problem of ∫cos^(3)x by parts. I have no idea how to integrate this. I know that I need to change the way I write cos^(3)x and I have seen people put cosx(1-sinx).

Please could you let me know where to find these equivilent ways of writing trigonomic formula? I assume there must be a table or something?

Thanks,

Andy

PS Sorry if this isn't the clearest explanation.

2. Relevant equations

3. The attempt at a solution

2. Oct 4, 2011

### SammyS

Staff Emeritus
I think you mean that cos3(x) = cos(x){1-sin2(x)} .

That's because sin2(x) + cos2(x) = 1 .

3. Oct 4, 2011

### Andyb43

You're probably right. This is the problem I'm having, I don't know what the equivalent expressions are.