Question

решите пожалуйста, очень срочно 2cos²3β-cos6β

Answer 1

$2cos^23\beta -cos\, 6\beta =(1+cos\, 6\beta )-cos\, 6\beta =1\\\\ili\\\\2cos^23\beta -cos6\, \beta =2cos^23\beta -(cos^23\beta -sin^23\beta )=cos^23\beta +sin^23\beta =1\\\\\\\boxed {cos2\alpha =2cos^2\alpha -1}\; \; \; \; \boxed {1+cos2\alpha =2cos^2\alpha }\; \; \; \boxed {sin^2\alpha +cos^2\alpha =1}\; \; \alpha =3\beta$