# How do you find the general solutions for #cos (x)^4-sin (x)^4=2*cos (x)*cos(2x)#?

##### 1 Answer

Oct 19, 2015

There are **6 solutions** over the interval

#### Explanation:

I'll exclude the variable x for simplicity:

Now simplify:

Now, we have 3 factors, when set equal to 0, will give us two unique solutions each for a total of 6 solutions over the interval

Again, the general solution is simply adding/subtracting multiples of

hope that helped