00:01
Okay, so we're going to let p of xy does denote a point where the terminal angle meets the unit circle.
00:07
And we're going to evaluate the six trigonometric functions of theta.
00:12
Given that p is in quadrant 4, so this is 1, 2, 3, 4, and that y equals negative a over 4.
00:29
So if y is negative a over 4, then i'm going to be somewhere like right here, where we have an unknown x and y.
00:37
Is negative a over 4.
00:43
We know that there's going to be a radius equal to 1 here.
00:47
So we need to find our other values.
00:49
So here's 1.
00:50
Here's negative a over 4.
00:53
And so this guy right here, our unknown, we're going to use pythagorean theorem to figure it out.
01:00
So 1 squared equals negative a over 4 squared plus our unknown value for that x.
01:07
So we're going to say that's x squared.
01:10
So we're going to have 1 squared minus a squared over 16 equals x squared.
01:18
So we take the square root of 1 minus a squared over 16.
01:24
That's going to be our value of x.
01:27
All right, so only cosine is here...