Question

Indicate the correct alternative(s), for $0<\varphi <\frac{\pi }{2}$, if $x=\sum _{n=0}^{\infty }{\cos }^{2n}\varphi ,y=\sum _{n=0}^{\infty }{\sin }^{2n}\varphi$ and $z=\sum _{n=0}^{\infty }{\cos }^{2n}\varphi {\sin }^{2n}\varphi$, then

• A. $xyz=xz+y$
• B. $xyz=xy+z$
• C. $xyz=x+y+z$
• D. $xyz=yz+x$

Answer 1

The correct option is B $xyz=xy+z$

Option (B) is the correct answer