SOLUTION: What's the Exact Value for Sin 13π/12 degrees ? Without using a calculator

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Question 577644: What's the Exact Value for Sin 13π/12 degrees ? Without using a calculator
Found 3 solutions by josmiceli, KareemM, Alan3354:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+sin%28+%2813%2Api%29%2F12%29+
+%2813%2Api%29%2F12+ = +%2812%2Api%29%2F12+%2B+%281%2Api%29%2F12+
+%2812%2Api%29%2F12+=+pi+
+pi+%2B+pi%2F12+ is in the 3rd quadrant where
the sine is negative
In degrees, +pi%2F12+=+180%2F12+
+180%2F12+=+15+ degrees
The answer is +-+sin%2815%29+
( I don't have a calculator )

Answer by KareemM(1) About Me  (Show Source):
You can put this solution on YOUR website!
Thank you sir, God Bless you

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
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-sin(15) =~ -0.258819
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For the exact value:
-sin(15) = -sin(30/2)
= -sqrt%28%281+-+cos%2830%29%29%2F2%29
= -sqrt%28%281+-+sqrt%283%29%2F2%29%2F2%29
= -sqrt%282+-+sqrt%283%29%29%2F2