00:02
All right, we want to prove this identity to be true.
00:05
We're going to show the left side is the same as the right side.
00:08
And we're going to start by working on the left side.
00:12
Now, the first thing i'm going to do, i'm going to take these two fractions that are on the left side, and i'm going to find a common denominator.
00:21
The common denominator is going to have to be sine theta times cosine of theta.
00:36
There's nothing i can do to change those to be like each other, so the best we can do is multiply them by each other.
00:44
That means then that i'm going to have to multiply the first fraction by cosine theta over cosine theta.
00:54
And the second one is going to get multiplied by sine theta over sine theta.
01:00
So now if we distribute the cosine data in that first fraction, we get sine theta, cosine, plus cosine square theta.
01:15
And in the second one, when we distribute the sign, we get sine theta, cosine theta, minus sine squared data.
01:34
And now, when i go to combine these two fractions, which is the reason why we wanted a common denominator, sine cosine minus sine cosine is zero.
01:47
And then we're going to have minus a negative sign...