00:01
Solve the equation 2 -theta plus 2 -sign theta equal 0 for theta between 0 degrees and 360 degrees.
00:07
So, first thing we're going to do is a substitution for sine 2 -theta, which is one of our double -angle formulas.
00:15
So, sine 2 -theta is equal to 2, sine theta, and then we'll bring down the plus 2, sine theta, and that's going to be equal to 0.
00:29
Both terms have sign in them, so we'll factor out sine theta.
00:35
So we have sine theta, and we're left with two cosine theta plus one, and that's equal to zero.
00:45
So we have two equations to solve.
00:49
We have to solve sine theta equals zero, and we have to solve two cosine theta plus one equals zero.
01:00
So for the left side, we're finding all the values of theta between 0 and 360, where sine is equal to 0.
01:11
So we remember the sign graph looks like this.
01:16
So the angles between 0 and 360 for which sign theta is equal to 0 are 0 degrees, 180 degrees, and 360 degrees.
01:28
So theta is equal to 0 degrees, 180 degrees, and 360 degrees.
01:41
We have to solve 2 cosine theta plus 1 equals 0, so we'll subtract 1 from both sides.
01:47
And we get 2 cosine theta equals negative 1.
01:52
We'll divide by 2...