Question

For △ABC, what is the value of cosC?


0.5
0.6
0.8
0.9

Answer 1

what is the ratio for cosine? which two sides?

Answer 2

idk

Answer 3

cos = adjacent over hypotenuse.
cos(angleC) = 72/90
angleC = inverse cosine(72/90)
Thus, angleC = 0.64350110879328
Cos(0.64350110879328) = .8

Answer 4

check out the Kahn Academy videos on trig
the first one is the best 7 minutes I have ever spent listening to a trig explanation

Answer 5

If you wanna be more elegant about it...

--> cos(arccos(4/5) = .8