Question

sin^4(π/12) - cos^4(π/12)

Answer 1

$sin^4frac{pi}{12}-cos^4frac{pi}{12}=(sin^2frac{pi}{12}-cos^2frac{pi}{12})(sin^2frac{pi}{12}+cos^2frac{pi}{12})=\\=-(cos^2frac{pi}{12}-sin^2frac{pi}{12})=-cosfrac{pi}{6}=-frac{sqrt3}{2}$