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August 20, 2014

August 20, 2014

Posted by **Denise** on Sunday, May 9, 2010 at 12:37pm.

- trig -
**Reiny**, Sunday, May 9, 2010 at 1:50pmSo sinx = 1/2 and x must be in 2nd quadrant.

then by Pythagoras cos x = -√3/2

we know cos 2A = 1 - 2sin^2A

then cosx = 1 - 2sin^2(x/2)

-√3/2 = 1 - 2sin^2(x/2)

2sin^2(x/2) = 1 + √3/2

sin^2(x/2) = (2 + √3)/4

sin(x/2) = (√(2+√3))/2

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