I came across this formula in some online resources.
$$r_{12.34} = \frac {r_{12.3} - r_{14.3}r_{24.3}}{ \sqrt {(1- r_{14.3}^2 )(1-r_{24.3}^2 }}$$
I can use this but I wanted a proof of the formula. Can you prove the formula or please direct me to any link with a proof?
