00:01
Okay, i want to find tan of inverse cosine negative 530s.
00:05
So let's call this item here a.
00:09
So i want to find then the value of tan a somehow.
00:14
Well, if a is inverse cosine of that number, that means cosine of a must be negative 5 over 13.
00:25
Now, you have to know that the range of the inverse cosine function is from 0.
00:32
To pi only and since it's negative it has to be in the second quadrant.
00:41
In other words, a would be that angle there.
00:46
So i'm just draw it again.
00:53
Here is angle a in the second quadrant.
00:57
Let's have alpha as my reference angle.
01:01
I know that cosine of a is negative, cosine of alpha...