10-3 Double-Angle and Half-Angle Formulas

For the following problem, one would use the formula Cos2alpha = cos^2alpha - sin^2alpha, 1-2sin^2alpha or 2cos^2alpha - 1

2 cos^2 pie/8 - 1
Notice that pie/8 is in the place of alpha, which means pie/8 is your alpha. In this chapter all you are doing is replacing so you would replace that part of the formula with what it is equal to; though first you would want to change pie/8 to degrees and get 45degrees. Once this is done you replace with the formula and get cos 2(45) and that is equal to cos(90), which is equal to 0. (Final Answer)

~ Parrish Masters