00:01
So using this diagram here, we're told that b is a point of tangency.
00:05
And they also give us this right angle here.
00:07
So we're going to use the pythagorean theorem to find out what r is.
00:11
So i have a squared plus b squared is equal to c squared.
00:16
And so for a, i'll use 30 squared.
00:19
And then b will be r squared.
00:22
And then c is going to be 18 plus r.
00:26
So i have 18 plus r.
00:29
Or you can always do, if you'd like, we can do r plus 18 squared.
00:37
So squaring this, i get 900 plus r squared.
00:41
And then i have to foil this...
