SOLUTION: evaluate the trigonometric fun sin 9pi/ 4 using its period as an aid.

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Question 588902: evaluate the trigonometric fun sin 9pi/ 4 using its period as an aid.
Answer by Edwin McCravy(20066) About Me  (Show Source):
You can put this solution on YOUR website!
sin(x) has a period of 2p, so we may add 2p to or subtract 2p 
from any angle as many times as we please and the sine of the 
resulting angle will be the same.

Therefore 

sin(expr%289%2F4%29pi) = sin(expr%289%2F4%29pi-2pi) = sin(expr%289%2F4%29pi-expr%288%2F4%29pi) = sin(expr%281%2F4%29pi) = sin(pi%2F4) = sqrt%282%29%2F2 

Edwin