# Homework Help: Difficult integral

1. Mar 20, 2007

### alba_ei

1. The problem statement, all variables and given/known data
$$\int \frac{\sin x+\cos x}{\sec x+ \tan x}dx$$

2. Relevant equations

$$\sin x = \frac{1}{\sec x}$$
$$\cos x = \frac{\sin x}{\tan x}$$

3. The attempt at a solution
i separate and try to use identities but i got nothign

1/(secx^2+secx tan x)+sin x/tanx^2+sec x

Last edited: Mar 20, 2007
2. Mar 20, 2007

### mjsd

write everything in terms of sin x and cos x only, then integrate with change of variable.

3. Mar 20, 2007

### cristo

Staff Emeritus
One of your identities is incorrect: sec(x)=1/cos(x).

As has been said above, you should first look to express everything in terms of sines and cosines. See if this gives you a hint as to how to proceed.

4. Mar 21, 2007

### Buddy J.

this is the shape that i got
don't know how to complete

–integral sin²x-sin2x-1/2(1+sinx)

5. Mar 22, 2007

### Gib Z

$$-(\int \sin^2 x dx - \int \sin 2x dx - 1/2\int 1+\sin x)$$

Write sin^2 x as (1/2) (1-cos2x).

for sin 2x, make a substitution u=2x, then remember the integral of sin u is -cos u.

For the 3rd one, if you can't do it, why are you doing this question?

6. Mar 24, 2007

### Qyzren

you can also try weierstrass substitution
i.e t = tan x/2