another identities NOT on formula booklet but can be derived easily anyway: (^ means squared)
sin2a = 2sinacosa
cos2a = 2cos^ - 1 , 1 - sin^a , cos^a - sin^a
tan2a = 2tana / 1 - tan^a
sec^a = tan^a + 1
cosec^a = cot^a + 1
????
also, any trig differentials not in formula booklet?