Question

cos(pi/12)
помогите, пожалуйста

Answer 1

$\cos \dfrac{\pi}{12}=\cos \left(\dfrac{\pi}{3}-\dfrac{\pi}{4}\right)=\cos \dfrac{\pi}{3}\cos\dfrac{\pi}{4}+\sin\dfrac{\pi}{3}\sin\dfrac{\pi}{4}=\dfrac{1}{\sqrt{2}}\cdot \left(\dfrac{1}{2}+\dfrac{\sqrt{3}}{2}\right)=\\ \\ \\ =\dfrac{1+\sqrt{3}}{2\sqrt{2}}$