SOLUTION: dertemine proper sign and actue angle need to complete the following equation cos31pi/5=?

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Question 475686: dertemine proper sign and actue angle need to complete the following equation cos31pi/5=?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
If the problem was +cos%2830%2Api%2F5%29+, that equals
+cos%286%2Api%29+. Even multiples of pi equals
0 degrees. There is a +pi%2F5+ left over, so
the angle is in the 1st quadrant, and cosine is positive.
+pi%2F5+=+36 degrees.