00:01
I'm given a trig ratio that is cosine of theta is one fifth.
00:04
We're asked to first of all draw a right angle with theta in it.
00:08
So i'll do that first.
00:11
So here's theta.
00:11
I'm going to put theta there.
00:13
There's my right angle.
00:14
So cosine is adjacent over hypotenuse.
00:19
So that means the adjacent side is going to be one.
00:21
This is the adjacent side here.
00:23
And the hypotenuse is going to be five.
00:25
So this is one.
00:27
This is five, which makes this, the square root.
00:35
5 squared minus 1 squared, okay, using the pythagorean theorem.
00:40
So that's the square root of 25 minus 1, which is the square root of 24, and that reduces to 4 times 6.
00:48
So that gives me 2 root 6.
00:50
So that side is 2 root 6...