Question

If cos(theta) = (-8/17) and sin(theta) = (-15/17) what quadrant is and cos(2theta)

Answer 1

have a look at this trig cheat sheet (with many formulas/identities you'll use in trig)

http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet.pdf

Answer 2

focus on the "double angle formulas"

Answer 3

Im still not understanding what quadrant its in

Answer 4

I sont know that range for this

Answer 5

cosine is negative in quadrants II and III (ie when x is negative)

Answer 6

sine is negative in quadrants III and IV (when y is negative)