00:02
So we're asked to solve the equation, cosine of negative theta equals root 5 over 5.
00:08
And they give us this extra piece of information that says the tension of theta must be less than 0.
00:14
So in order to first solve this, we need to use your calculator because our calculator continued the inverse cosine button.
00:24
So in order to cancel out the cosine on the left side right here, we need to apply the inverse cosine to it.
00:32
So essentially, if we apply inverse cosine on the left side, we can also apply it on the right side.
00:48
And so these cosines on the left will cancel out.
00:52
If you have a ti -84 calculator, the inverse cosine button, is right above the cosine button.
00:58
So you press second to press cosine.
01:02
So inverse cosine of root 5 divided by 5.
01:13
And this should come out to 1 .107 radians.
01:28
But we have to eliminate the negative, so we multiply both sides of this equation by negative 1, just like this, and our final value for theta is negative 1 .107.
01:51
But we still need to incorporate the fact the tangent of data is less than 0.
01:56
So we know that data equals negative 1 .107.
02:01
We can plot this on a little graph.
02:04
So here's the graph of all of our angles, starting at zero radiance, pi radians, and then circling back again to zero as two pi radians.
02:13
So negative 1 .107, if we divide that by pi, we can find a way to put that onto our graph...