Pr:

Consider a quadrilateral MNOL in which the diagonals are equals and bisecting each other at I
We have

∴ I is the center of symetry of the figure ,MNOL is a //gramm and we have:

Also the 2 triangles MLO and MLN are congruent since:

∴ they are congruent according to the case S.S.S
and

M =

L and the 4 angles of the quadrilateral are equal,each to 90⁰.
Finally MNOL is a rectangle .

Grade |

Definition and Properties of the rectangle.