If the cosine of the angle between the vectors $a$ and $b$ is $x$ and the cosine of the angle between the vectors $a$ and $p$ is $y$, then, if we call $z$ the cosine of the angle between the vectors $b$ and $p$, can we write $z$ in terms of $x$ and $y$?
All vectors are in $4$-dimensional Euclidean space.