00:01
So we want to evaluate this expression as a single fraction without a calculator.
00:06
And so these are all angles that we can figure out the sign and cosine of without technology.
00:14
And so let me just quick write this down.
00:18
And then we'll think, i believe that's three pi over two.
00:21
Okay.
00:23
So we quick draw a unit circle.
00:27
And we know that pi over three, pi over three is equivalent to 60 degrees.
00:33
And so we want up here, if we draw that little reference triangle, and if that is the 60 degree angle, we know that this side is one half.
00:44
This side is square root of 3 over 2.
00:47
And so the sign of the angle is square root of 3 over 2.
00:52
And then we'll figure out that in a second, minus, and the cosine is the 1 1⁄2.
00:58
And again, we'll figure out that in a second.
01:00
So now let's go to the next angle.
01:03
The next angle is pi.
01:05
Go that in red.
01:06
So pi is right here.
01:08
And that coordinate on the unit circle is negative 1 .0...