00:01
We're trying to prove that the identity on the left is going to match up with the identity on the right.
00:05
So we're given the 1 minus sine squared over sine squared is equal to cotangent squared.
00:10
So the very first thing we see here is we're changing 1 minus sine squared into cosine squared.
00:15
So it becomes cosine squared of alpha over sine squared of alpha.
00:20
And then this is our pythagorean identity.
00:24
Because the pythagorean identity is cosine squared plus sine squared is equal to 1.
00:30
So in that drop -down menu, there's probably something in there that says pythagorean identity.
00:36
So it looks like the next thing they did was simplified by spreading things apart.
00:41
So this was cosine alpha over sign of alpha times.
00:47
Cosign alpha over sign of alpha.
00:52
So the property there is by simplifying...