00:01
Solve the following trigonometric equation.
00:03
Now it says, i wrote it down wrong, let's put 7 cosine theta here, 7 cosine theta.
00:08
So i'm going to get rid of the 2 theta and i want to use the identity 2 cosine squared theta minus 1 for the cosine because i need, want to keep my cosine thetas.
00:19
And at the same time i'm going to set it equal to 0 by subtracting 8.
00:23
So i'm going to have 2 cosine squared theta plus 7 cosine theta minus 9 equals to 0.
00:31
Now let's see if this will factor.
00:33
2 cosine theta, cosine theta.
00:37
So i need factors of 9 that are going to work in there and give me a 7.
00:43
Let's solve them and that'll be if i have a 9 and a 2...