00:01
So for this problem, we're working with the unit circle.
00:03
And they tell us that we have a point on the unit circle in the fourth quadrant.
00:08
So that's going to be somewhere in here.
00:13
And that the point is 1517s, comma, y, and we need to figure out why.
00:24
So one thing that's important about the unit circle is that every point that makes up this circle represents cosine comma sine.
00:37
Okay, so this point here, whatever y is will be sign, and i already know cosine.
00:48
So if i make a right triangle out of the unit circle at that point, here's my right triangle.
01:02
Like i said, i know that this represents cosine, so 15 over 17.
01:07
So thinking about this angle right here, cosine is a over h or adjacent over hypotenuse.
01:20
So adjacent to this angle would be this side here.
01:25
So that would be 15...