General Formulas for Review

a = alpha
b = beta

cos(a +- b) = cos(a)cos(b) -+ sin(a)sin(b)
sin(a +- b) = sin(a)cos(b) +- cos(a)sin(b)
tan(a + b) = tan(a) + tab(b)/ 1 - tan(a)tan(b)
tan(a - b) = tan(a) - tab(b)/ 1 + tan(a)tan(b)

sin2a = 2sin(a)cos(a)
cos2a = cos^2(a) - sin^2(a)
          = 1 - 2sin^2(a)
          = 2cos^2(a) - 1

tan2a = 2tan(a)/ 1 - tan^2(a)

sin a/2 = +- square root of (1 - cos(a)/2)
cos a/2 = +- square root of (1 + cos(a)/2)
tan a/2 = +- square root of (1-cos(a)/ 1 + cos(a))
           = sin(a)/ 1 + cos(a)
           = 1 - cos(a)/ sin(a)

~ Parrish J. Masters Jr.