Dedicate yourself and you will find yourself
\[ s = 1- \cos a + \cos^2 a - \cos^3 a + \cdots \\ r = 1-\sin a + \sin^2 a - \sin^3 a + \cdots \]
We are given the two equations above. State the expression below in terms of \(r\) and/or \(s\).
\[ 1 - \sin a \cos a + \sin^2 a \cos^2 - \sin^3 a \cos^3 a + \cdots \]