Question

Exercitiul 10 va rog. As vrea sa il si explicati ca sa inteleg acest tip de exercitiu. Multumesc! :)

Answer 1

$E=cos^4 \frac{7 \pi }{12}+sin^4 \frac{7 \pi }{12}=(cos^2 \frac{7 \pi }{12}+sin^2 \frac{7 \pi }{12})^2-2sin^2 \frac{7 \pi }{12}cos^2 \frac{7 \pi }{12}= \\ =1^2- \frac{sin2* \frac{7 \pi }{12} }{4}=1-(- \frac{ \frac{1}{2} }{4}) =1- \frac{1}{8}= \frac{7}{8}$