00:01
We are asked to find the reference angle of the given equation.
00:05
We are asked to...
00:06
And to do that, we'll first draw the unit circle.
00:15
And recall that the values of sine are on the y -axis.
00:20
And this corresponds to y equals negative 1.
00:23
And negative 0 .66 will be probably somewhere here, in that region.
00:32
So and that gives us two solutions for the equation.
00:39
But first we need to find the reference angle.
00:42
And it's basically the measure over the angle to the x -axis.
00:50
So it's going to be this angle here.
00:52
This is the reference angle.
00:55
And to get that angle, we'll first apply arc cos to both sides of the equation.
01:00
We'll get theta equals arc...
01:02
Sorry, arc sine.
01:04
Arc sine of negative 0 .66, which is approximately...