a: \(M=\dfrac{1}{tana+cota}=1:\left(\dfrac{sina}{cosa}+\dfrac{cosa}{sina}\right)\)
\(=1:\dfrac{sin^2a+cos^2a}{cosa\cdot sina}=cosa\cdot sina=\dfrac{2\sqrt{2}}{9}\)
b: \(A=\left(sin^2a+cos^2a\right)^3-3\cdot sin^2a\cdot cos^2a+3\cdot sin^2a\cdot cos^2a\)
=1