Ineed with any but 14. it’s trig identities

Short 2

(Sin(x) - Cos(x) )^2 = sin^2(x) - 2 sin(x)*cos(x) + cos^2(x)
(sin(x) + cos(x) )^2 = sin^2(x) + 2sin(x)*cos(x) + cos^2(x)  Add these two
2sin^2(x) + 2cos^2(x)  is all that is left. The two middle terms cancel out

Take out the common factor of 2
2(sin^2(x) + cos^2(x) ) 
but sin^2(x) + cos^2(x) = 1

2 * 1 = 2
2 <<<< answer