SOLUTION: I need help using the unit circle. The Question is find the exact value of cos(-13pi/4)

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Question 933012: I need help using the unit circle. The Question is find the exact value of cos(-13pi/4)
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
Proper form is found by adding multiple if 2pi
4pi+=+%2816%2F4%29pi
cos(-13pi/4) = cos(-13pi/4 + 16pi/4) = cos(3pi/4) = -√2 /2
........
(cosx, sinx) Summary Unit Circle
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