00:02
For this problem we're just trying to find these different exact trig values.
00:08
You can do that using the unit circle.
00:15
I'm just going to sketch a quick one.
00:16
This over here is going to be 1, 0.
00:20
And then we've got 0, 1.
00:24
Negative 1, 0.
00:27
0, negative 1.
00:29
And then just the first quadrant, we've got pi over 4, pi over 6, and pi over 3, pi over 4.
00:41
Remember the coordinates are square root 2 over 2, square root 2 over 2.
00:47
At pi over 3 our coordinates are 1 half, square root 3 over 2.
00:54
Here our coordinates are square root 3 over 2, 1 half.
01:00
And so we can use this to find all these other values.
01:03
So the sine of negative pi over 6.
01:06
Negative angles just go down instead of up.
01:10
That's how we count them.
01:12
So negative pi over 6 is this angle right here.
01:15
So it's got the same coordinates as pi over 6, except our y value is negative.
01:21
We've got a positive x, negative y.
01:23
So the sine is just the y value.
01:29
So the y value at negative pi over 6 is going to be negative 1 half.
01:37
Negative pi, same thing.
01:39
We're going to swing this way down pi degrees, or radians.
01:47
So pi is halfway around.
01:50
So this over here is negative pi...