Докажите тоджество: sin^2 (a+B) — sin^2 (a-B)=sin 2a sin2B

sin^2 (a+B) — sin^2 (a-B)=sin 2a sin2B (sin (a+B) — sin (a-B)*(sin (a+B)+sin (a-B)=sin 2a sin2B (sina*cosB+sinB*cosa-sina*cosB+sinB*cosa)*(sina*cosB+sinB*cosa+sina*cosB-sinB*cosa)=sin 2a sin2B2sinB*cosa*2sina*cosB=sin 2a sin2Bsin 2a sin2B=sin 2a sin2B