00:02
So sine of a is 2 3rds, and i'm told a is in quadrant 2.
00:11
So opposite hypotenuse, you can find that missing third side just using pythagorean theorem.
00:21
So 9 minus 4 is just 5.
00:24
So that side is rad 5, which tells me the cosine of a is negative rad 5 over 3.
00:32
Now i'm told cosine of b is negative 1 4th, and b is also in quadrant 2.
00:46
So x squared plus 1 squared is 4 squared.
00:51
So that's going to give me 15.
00:54
So that's the square root of 15.
00:57
The sine of b is going to be positive square root of 15 over 4.
01:03
Now i want in a the sine of a minus b.
01:10
So that's sine of a cosine of b minus cosine a sine b.
01:18
So sine of a is 2 3rds.
01:22
Cosine of b is negative 1 4th...