SOLUTION: using the periodic properties of trigonometric functions find the exact value of the expression cos(8<font face="symbol">p</font>/3)?

Algebra ->  Trigonometry-basics -> SOLUTION: using the periodic properties of trigonometric functions find the exact value of the expression cos(8<font face="symbol">p</font>/3)?       Log On


   

Question 373947: using the periodic properties of trigonometric functions find the exact value of the expression cos(8p/3)?
Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
cos%288pi%2F3%29
cos%28expr%288%2F3%29pi%29
cos%28expr%282%262%2F3%29pi%29
cos%28%282%2B2%2F3%29pi%29
cos%282pi%2Bexpr%282%2F3%29pi%29%29
cos%28expr%282%2F3%29pi%2B2pi%29
By the fact that the period of cosine is 2pi, the above equals
cos%28+++expr%282%2F3%29pi++%29
and that's the same as 2pi%2F3 or 120°, a second quadrant
angle which has a cosine of
-1%2F2
Edwin