The resultant force, R, is related to two concurrent forces, X and Y, acting at right angles to one another, by the formula R^2 = X^2 = Y^2 . Rewrite the formula for Y.
The two forces X and Y are acting at right angles which means the value of the resultant R is hypotenuse of the right triangle with X and Y as legs. This means R is governed by Pythagorean theorem:
R^2 = X^2 + Y^2
Rewriting in terms of Y
Y^2 = R^2 – X^2
Y = sqrt(R^2 – X^2)
