SOLUTION: Use trigonometric identitets to find the trigonometric function value of x, given that sin=-1/3 and x is in quadrant III. cos x = ?.

Algebra ->  Trigonometry-basics -> SOLUTION: Use trigonometric identitets to find the trigonometric function value of x, given that sin=-1/3 and x is in quadrant III. cos x = ?.      Log On


   

Question 969087: Use trigonometric identitets to find the trigonometric function value of x, given that sin=-1/3 and x is in quadrant III.
cos x = ?.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
sin%5E2%28x%29%2Bcos%5E2%28x%29=1
1%2F9%2Bcos%5E2%28x%29=1
cos%5E2%28x%29=8%2F9
cos%28x%29=0+%2B-+sqrt%288%29%2F3
Since cosine is negative in Q3,
cos%28x%29=-%282%2F3%29sqrt%282%29