# Integrals of Trigonometric Functions

1. Sep 20, 2009

### recon_ind

I have three problems that I'm having a hard time with. I'd appreciate any help with
any of the three problems.

$$\int((cos(x))^6)dx$$

AND

$$\int(x^3 * sqrt(x^2 - 1)$$

AND

Solve for y (separation of variables):
dy/dx = ((2y + 3)^2)/((4x + 5)^2)

THANKS soo much.

2. Sep 20, 2009

### lurflurf

first one reduction formuls or integration by parts (integrate cos(x) differentiate cos(x)^5)
second one substitute x^2-1->w
third one just separate and integrate