00:01
I want to find the exact value.
00:02
I think a little bit clearer in degrees, so i'm going to convert 5 pi over 12, 2 degrees, by multiplying by 180 over pi.
00:15
That is going to give me negative 75 degrees.
00:20
And it doesn't matter whether you work in degrees or radiance.
00:24
The sign of 30 degrees is a half.
00:27
The sign of pi over 6 is a half.
00:29
So use whichever is more comfortable to you.
00:34
Negative 75 degrees, first of all, is in quadrant 4.
00:40
So when i'm choosing which version of my half angle formula, because remember you have two, you have a positive and a negative.
00:51
It's going to be 1 minus cosine theta over 2.
00:55
We're going to choose the negative root because sine is negative.
01:04
Negative in quadrant 4, and it's the half angle that determines the positive or the negative to use...