Given the function \(f(x) =\cos x -\sin x\), find its primitive function F so that the graph of \(F\) passes through the point \(A = \left [ \pi,3\right ]\).
Find the intersection of the line \(KL\)
and the line \(q\),
where \(K = [1,3,5]\),
\(L = [3,-2,4]\) and
\[
\begin{aligned}q\colon x& = 1 + r, &
\\y & = 5 - 2r,
\\z & = 3 - r,\ r\in \mathbb{R}.
\\ \end{aligned}
\]