Exercise 16 let ABCD be a square of side 5 cm. let I be the midpoint of (AD)and J that of (BC) 1 prove that IB=IC
2 a) show that ABJI is a rectangle
b) Deduce that AJ=IC
3 let E be the midpoint of (DC) let L be the symmetry of J with respect to C and F be the symmetry of E with respect to C

Google it that might work

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .