00:01
So recall the different quadrants that i have.
00:02
I have my first quadrant, my second, my third, and then my fourth.
00:08
So let's suppose i drew, i know cosine of an angle t equals negative 7 over 25.
00:14
So in my third quadrant, i can draw a right triangle with an angle, acute angle, theta, or t.
00:22
What ratio is cosine? cosines adjacent over hypotenuse, right? one way to remember my trig ratios is the acronym sokotoa.
00:30
Cosines adjacent.
00:32
So the adjacent side is 7 and the hypotenuse is 25.
00:37
But notice i have a negative.
00:38
Does negative go to the 7 or the hypotenuse? hypotenuse is always positive, so it's going to go to the negative 7, also because my x values are negative.
00:47
Now, before i do anything else, let's figure out the third side of my triangle.
00:52
How do i do that? when i write triangle, this is a b value, to find the third side, i'm going to do my pythagorean theorem.
01:02
Negative 7 times negative 7 is positive 49 equals 25 times 25, 625.
01:10
And what i could do is subtract 49 from both sides...