Question

Calcule y= cos² pi/12 - sen² pi/12 . Alguém sabe?

Answer 1

$\displaystyle y=\cos^2{\frac{\pi}{12}}-\sin^2{\frac{\pi}{12}}=\cos{\left(2\cdot\frac{\pi}{12}\right)}=\cos{\frac{\pi}{6}}=\frac{\sqrt{3}}{2}$