00:01
Okay, we have here cosine negative and cot negative.
00:05
And this implies, since cot is 1 over tan, that means tan also is negative.
00:13
Now, to have cosine negative and tan negative, you must be in the second quadrant.
00:19
It's the only place where those two things occur, so i'm here.
00:26
So my angle theta must be that angle, which means my reference angle, alpha, is here.
00:35
Let's draw a triangle then.
00:38
So i know cosine theta will equal negative cosine alpha.
00:45
So minus two thirds is minus caus alpha.
00:51
So cos alpha is two alpha is two over three, which means here is two adjacent and often use three...