00:01
Okay, we are given some information and we are asked to find the remaining trigonometric functions.
00:08
So one bit of information that we're given is that theta is between zero and two, i'm sorry, not two, but pi over two.
00:16
So theta is between zero and pi over two.
00:20
So what that means, if i look at a cartesian plane, that means that i have to be here in quadrant one.
00:28
It's important to know that because as i go through and i'm figuring out what my trig functions are, i need to know are they positive or negative.
00:39
Well, in quadrant one, everything is positive.
00:42
So that's good to know.
00:44
Now, the other thing we're given is that cosine theta is equal to two nights.
00:50
So there's one.
00:51
We've got cosine theta right away.
00:53
So that also gives us secant theta, because secant is simply the reciprocal.
00:58
Of cosine, equal sign.
01:02
But that secant, because of cosine of theta is two nints, then the secant of theta is nine over two.
01:09
So there's a couple of ways that you can go about this.
01:12
I'm going to use a trig identity, because one identity i know is that cosine squared plus sine squared is equal to one.
01:24
So i already know what cosine is.
01:26
It's given to me right there.
01:28
So two nights squared.
01:31
Plus sine squared is equal to 1.
01:35
So this is going to be 4 over 81, and 1 is the same as 81 over 81.
01:48
So i'm going to subtract this 4 over 81, so that i have sine squared theta is equal to 81 minus 4 would be 77 over 81...