00:01
Okay, first step here, like terms together.
00:03
So we have 2, cosine 2 theta equals 2.
00:09
Just add cost 2 theta to both sides.
00:13
Then divide by 2 on both sides.
00:18
Now we get root 2 over 2, the cosine 2 theta.
00:23
Now, this should ring a bell.
00:27
It's triangle 1 -1 root 2.
00:29
So 45, 45, 90.
00:32
Is the triangle or pi by four, pi by four, pi by two.
00:40
Now, where is cosine plus? it's the first and the fourth quadrant.
00:48
And the reference angle is 45 degrees or pi by four.
00:54
So pi by four goes here.
00:57
And so from that grid, i can now read off the answers...
