Reciprocal Identities
1. cscx=1/sinx
2. secx=1/tanx
3.cotx=1/tanx

Pythagorean
1. sin^x + cos^x =1
2. tan^x +1 = sec^x
3. 1 + cot^x = csc^x

Sum and Difference
1. Cos(A-B) = Cos A Cos B + Sin A Sin B
2. Cos(A+B) = Cos A Cos B - Sin A Sin B
3. Sin(A-B) = Sin A Cos B - CosASinB

Product to sum & sum to product
1. Sin A Cos B =1/2[sin(a+b)+sin(a-b)]
2. Cos A Sin B = 1/2[sin(a+b)-Sin(a-b)]