Question

$( \sin \alpha - \cos\alpha ) {}^{2} + 2 \sin \alpha \cos \\ \alpha$
​

Answer 1

(Sinα - Cosα)² + 2SinαCosα = Sin²α - 2SinαCosα + Cos²α + 2SinαCosα =

= Sin²α + Cos²α = 1