Looking for the equation to find the length of one side of a rectangle. I have the diagonal and one side of the rectangles numbers. How do I find the other side?

Pythagorean theorem. a^2 + b^2 = c^

so if i have a triangle with a side of 3cm and a diagonal of 5cm I plus the one leg (3) into a^2 and the diagonal (5) into c^2

3^2 = 9

5^2 = 25

9 + b^2 = 25

b^2 = 16

square root 16 which gives you 4