00:01
Okay, we need to simplify the sign of 2 times the cosine inverse of x.
00:20
I'm going to use one of my double angle formulas.
00:23
I know that the sign of 2 theta is 2, sine theta, cosine theta.
00:32
2xan theta, cosine theta.
00:41
Well, now my theta here, see the angle is right there, it's the inverse cosine of x.
00:51
That's my theta.
00:52
So i'm going to have 2 times the sign of cosine inverse, that's the angle whose cosine is x, and then times the cosine of my theta.
01:08
The angle here is cosine inverse of x.
01:16
I'm going to draw a picture to help me figure this out.
01:23
So here's the angle, and the cosine is x.
01:26
Remember, cosine is the side adjacent over the hypotenuse.
01:33
Now i can use pythagorean theorem to get this side.
01:37
That's going to be the square root of 1 minus x squared...