# What is the formula of diagonal of cube and cuboid?

A diagonal is a line segment that joins one corner to another but is not an edge. So we get a diagonal when we directly join any two corners (vertices) which are not already joined by an edge.

## Answer: Diagonal of a cube = 3⎷a , Diagonal of a cuboid = ⎷l^{2} + b^{2} + h^{2}

Let's look into the expressions of diagonal for a cube and a cuboid

## Explanation:

Let 'a' be the side length of a cube.

The diagonal of a cube is given by the formula 3⎷a

Let 'l' be the length, 'b' be the breadth and 'h' be the height of a cuboid.

The diagonal of a cuboid is given by the formula ⎷l^{2} + b^{2} + h^{2}

**Thus, Diagonal of a cube = 3⎷a , Diagonal of a cuboid = ⎷l**^{2} + b^{2} + h^{2}

^{2}+ b

^{2}+ h

^{2}