00:04
I'm going to draw a triangle a, b, c.
00:08
And let's say we have angle b is 10 degrees.
00:12
We know angle c is 100 degrees, and side c is 115.
00:17
Now we can easily find angle a because of the 180 factor.
00:22
All three triangles are three angles in any triangle have to add up to 180.
00:27
So if we did 180 minus 100 minus the 10, would give us the remaining angle, which was 70 degrees, for angle a.
00:39
And then we can use the law of signs.
00:45
And i'll change colors.
00:47
I'm going to set up the sign of 100 degrees over angle c, 100 degrees, over side c -115.
00:54
We call the sign of angle a, 70 degrees, over side a.
01:00
So if we cross -multify, we have a times the sign of 100.
01:05
Will equal the sign of 70 times 115...