Question 1036928
Find the exact value of each of the following. (Hint: you may need Angle Sum/Difference, Double Angle, or Half Angle Identities):

a. cos(13pi/12)


b. sin(pi/8)


c. tan(2X) if cosX = 5/6 and X is in Quadrant 1
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Look up "half angle formulas" on Wikipedia.
It's covered well there.