SOLUTION: Given that cos 80 = 0.173648... explain how to find cos100, cos260, cos280, and sin190 without using a calculator.

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Question 1146963: Given that cos 80 = 0.173648... explain how to find cos100, cos260, cos280, and sin190 without using a calculator.
Answer by ikleyn(52832) About Me  (Show Source):
You can put this solution on YOUR website!
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cos(100°) = -cos(80°) = -0.173648...


cos(260°) = cos(180°+80°) = -0.173648...


cos(260°) = cos(360°-80°) = cos(80°) = 0.17648...


sin(190°) = cos(190°-90°) = cos(100°) = -cos(80°) = -0.173648...


Answered and solved.