Some people find geometry branch of maths difficult, so in this paper, we have some easy solutions to finish this problem, the mind-set of the people. This problem should not to be ignored because every branch or every part of maths is important. Everywhere, maths is involved. In this paper, you will know some new formula for finding diagonal’s value of a quadrilateral having 90° in its vertices. Intersecting diagonals of a 90° quadrilateral will make the same amount of degrees after intersecting each-other. You will know 5 new formulas in this paper for the following situation.

Keywords : Polygon- A shape or a closed curve made up of line segments. Triangle- A polygon having 3 line segments as its sides. Quadrilateral- A polygon having 4 line segments as its sides.