Question

-2sin²(π/6 -aльфа)+6-2cos²(π/6- альфа)

Answer 1

$-2sin^2(\frac{\pi}{6}-a)+6-2\, cos^2(\frac{\pi}{6}-a)=\\\\=-2\cdot \Big (sin^2(\frac{\pi}{6}-a)+cos^2(\frac{\pi}{6}-a)\Big )+6=-2\cdot 1+6=4\\\\\\\star \; \; \; sin^2x+cos^2x=1\; \; ,\; \; x=\frac{\pi}{6}-a\; \; \star$