See a square is the only quadrilateral which has all the sides equal and the all the angles between any two sides is 90°, and so it also has the two diagonals intersescting at 90°.
The prove of the intersection of the two diagonals :
In a square the two diagonals intersect they form four (4) equal small triangles within that square , taking one square the diagonal joining the vertex of the two sides of the square bisects the angle i.e the 90° is bisected which is equal to 45° and the other part is also 45° ,Taking two angles i.e 45° and 45° and let the angle between the intersection of the diagonals be x°
Hence, it is also known the diagonals intersect at the mid point of each other so the each triangle is an isoceles
Then , in any of the triangle ,
⇒ x°=180°- 90°
⇒ x° = 90° Ans.
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