00:01
In this problem, we're being asked to find all the values of theta such that cotangent theta is equal to zero.
00:07
And we want to solve for all angles between zero and two pi.
00:11
Well, keep in mind, cotangent is reciprocal tangent, or you can think about it in terms of sine and cosine.
00:18
Well, cotangent is the cosine of theta divided by the sine of theta.
00:23
So because it's a fraction, we just need to know when our numerator is equal to zero, because then zero divided by anything would be equal to zero.
00:29
So really, we just need to figure out, well, when is cosine of theta equal to zero? well, if you think about your unit circle, cosine is associated with an x coordinate.
00:39
So we need to figure out when cosine is equal to zero.
00:42
We want to know when x is zero.
00:44
Well, that happens on our y -axis.
00:45
So thinking about our unit circle, that would happen at 90 degrees, or pi over 2, as well as 270 degrees, which would be 3 pi over 2...