SOLUTION: If cos&#952;=0.8 and 270<&#952; <360, find the exact value of sin2&#952; a. -0.96 b. -0.6 c. 0.96 d. 0.28 Is it A?

Algebra ->  Trigonometry-basics -> SOLUTION: If cos&#952;=0.8 and 270<&#952; <360, find the exact value of sin2&#952; a. -0.96 b. -0.6 c. 0.96 d. 0.28 Is it A?      Log On


   

Question 198569: If cosθ=0.8 and 270<θ <360, find the exact value of sin2θ
a. -0.96
b. -0.6
c. 0.96
d. 0.28
Is it A?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Recall that

So if , then . Plug this into the identity above to get:





Now solve for :







Now because , this means that the value of sine will be negative.


So this means that


Now recall the identity:


... Start with the given identity


... Plug in and


... Multiply


So which means that the answer is A) -0.96. So you are correct. Good job.