calculas problem

**Haris** · November 24th 2008, 08:08 PM

Find

.

Any help would be appreciated cheers x

**mr fantastic** · November 24th 2008, 08:14 PM

Originally Posted by Haris

Find

.

Any help would be appreciated cheers x

Substitute $u = 4 + \cos (y)$ .

**Chris L T521** · November 24th 2008, 08:14 PM

Originally Posted by Haris

Find

.

Any help would be appreciated cheers x

Let $z=4+\cos y\implies \,dz=-\sin y\,dy$

Thus, the integral transforms into $-7\int\frac{\,dz}{z}$

Can you take it from here?

**Haris** · November 24th 2008, 08:28 PM

I got -7ln(4+cos(y))+C but its wrong i think?

**mr fantastic** · November 24th 2008, 08:38 PM

Originally Posted by Haris

I got -7ln(4+cos(y))+C but its wrong i think?

Don't be so helpless. Try to differentiate it and see whether you get the integrand ....

Thread: calculas problem