Hi,

I have two questions I'd like some help with.

Firstly what is $\displaystyle \int cos^3 2x$ dx ?

I tried doing it with trigonometric identities for $\displaystyle cos 2x$ but it became very nasty pretty fast. Any help would be great.

Also, this has been bugging me all day, and I can't see where I am wrong, though I must be... Why is the integral of $\displaystyle \int \tfrac{2}{2x+3} dx = ln(2x+3) $ yet $\displaystyle \int \tfrac{1}{x+1.5} dx = ln(x+1.5) $

Because $\displaystyle \tfrac{2}{2x+3} = \tfrac{1}{x+1.5}$ yet $\displaystyle ln(x+1.5) $ is not the same as $\displaystyle ln(2x+3)$

What am I doing wrong?

Thanks.