00:01
We have to solve sine 2 theta minus cosine theta equal 0.
00:06
To solve this, we are going to use the substitution for this double angle right here.
00:16
So, sine 2 theta is equal to 2, sine theta, cosine data.
00:25
So we have 2 sine theta, cosine theta.
00:27
Then we're going to bring down the minus cosine theta.
00:30
And we're going to set that equal to 0.
00:34
Both of these terms have a cosine theta, so we're going to factor out.
00:38
Cosine theta, so it's going to be cosine theta times 2, sine theta minus 1 equals 0.
00:50
So we actually have two equations to solve.
00:54
We need to solve cosine theta equals 0, and we have to solve 2.
01:03
Sin theta minus 1 equals 0.
01:06
So for cosine theta equals 0, we're looking for the angles whose cosine are equal to 0.
01:15
Remember, the graph of cosine looks like this.
01:26
So the angles where cosine crosses through the x -axis, so where cosine is equal to 0 are 90 degrees and 270 degrees...