Question: what is the formula for finding the number of diagonals in a quadrilateral?
Answer: You can use this formula with any polygon to find out how many diagonals it has without having to draw and count all of them. The formula is n(n - 3)/2, where n is your number of sides. So, a rectangle has an n of 4 because it has 4 sides. Let's try this formula out to see it works.