SOLUTION: Express cos 71pi/11 as a function of a real number a where 0 < a < pi/2.

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Question 779175: Express cos 71pi/11 as a function of a real number a where 0 < a < pi/2.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You can subtract any multiples of +2%2Api+ without
changing the expression
Subtract +6%2Api++=+%2866%2F11%29%2Api+
+%2871%2F11%29%2Api+-+%2866%2F11%29%2Api+=+%285%2F11%29%2Api+
This is less than +pi%2F2+ since +5.5%2F11+=+pi%2F2+
-----------
+%28+5%2F11+%29%2Api+=+%28+5%2A3.141+%29+%2F+11+
+%28+5%2F11+%29%2Api+=+1.4277+
+cos%28+71%2Api%2F11+%29+=+cos%28+1.4277+%29+
This is the cosine of an angle in radians