Question

Алгебра................ ​

Answer 1

$y=-2\, cos\Big(\dfrac{1}{3}\, x-\dfrac{\pi}{20}\Big)\\\\\\T(cosx)=2\pi \ \ \ \Rightarrow \ \ \ T\Big(-2\, cos\Big(\dfrac{1}{3}\, x-\dfrac{\pi}{20}\Big)\Big)=\dfrac{2\pi }{1/3}=6\pi$