How Do You Find the Diagonal of a Rectangle? Do you know how to find the area of a square… Consider a square of sides “a” units and diagonal as “d” units. For example, if your rectangle is 3 cm wide and 4 cm long, square these numbers to get 9 and 16. Length of the diagonal. A rectangle has two diagonal and they are congruent, that is both will measure the same length. For example, if you are calculating the diagonal of a 5-centimeter square, your formula will look like this: = = So, the diagonal of the square is 7.07 centimeters long. Using a diagonal of a rectangle calculator makes the entire process effortless as long as you have other measurements, but you can also use the diagonal of a rectangle formula. Diagonals of polygons are also useful. This is the reason diagonals for a square are also equal. The formula to find the area of any square if its diagonals are given can be derived using Pythagoras theorem as explained below:. Its diagonals are: equal in length; perpendicular bisectors of each other; bisectors of square angles; Each diagonal divides the square into two congruent isosceles right triangles - 45 45 90 special right triangles. Add them to get 25, then find the square root of 25 to get 5. Example: Sam cuts grass at $0.10 per square meter How much does Sam earn cutting this area: Let's break the area into two parts: Part A is a square: Computer and television screens, doors, and sheets of paper are all polygons. Diagonal of rectangle refers to the line segment or straight line that connect the opposite corner or vertex of the rectangle. What is the formula of diagonal of square and rectangle Get the answers you need, now! Because the triangles are congruent, they have the same area, and each triangle has half the area of the square. getcalc.com's Square Formulas & Calculator is an online basic geometry tool to calculate area, perimeter, diagonal or side of a square shape or plane in both US customary & metric (SI) units. As you can see, a diagonal of a square divides it into two right triangles, BCD and DAB. Log in Join now Secondary School. Formula of rectangle diagonal in terms of sine of the acute angle between the diagonals and the area of a rectangle d = √ 2A : sin β. Then find the square root for it, the resultant value is the length of diagonal. Therefore, the measurement of the diagonal for your rectangle is 5 cm. Learn how to instantly know how many diagonals any polygon can have by using this formula: # In this case, the diagonals of a rectangle will bisect each other and they are congruent too.