00:01
All right, so what we have going on is we're in quadrant three, and they go ahead and give you that x is over here because it's cosine of x.
00:15
So that's your angle is equal to negative 15 over 17.
00:18
So what i would do is point out that the adjacent side of this right triangle would be negative 15.
00:23
The hypotenuse would be 17 because that's what cosine is adjacent over hypotenuse.
00:30
And so this coordinate has to be negative 8.
00:35
Negative because we're going down, and i know it's 8 because this is a pythagorean triple, that 8 squared plus 15 squared always equals 17 squared, right? 64 plus 225 always equals 289.
00:50
If you didn't know that, i would probably commit that to your memory of a pythagorean triple.
00:55
So we'd go through that because then sign of x is the opposite.
01:00
Over the hypogynes.
01:02
I'll even point that out opposite.
01:05
And the hypothesis is still 17.
01:07
So if we're asked to evaluate sine of 2x, what we would get is two, i'm just using the formula sheet, two sign of x, cosine of x.
01:19
So then when we're looking at it, we're at 2 sine of x as negative 8 over 17, cosine of x is negative 15 over 17...