Question 448087
Hint: A drawing really helps. Once you've drawn a general quadrilateral with four congruent sides (ie a rhombus), divide the quadrilateral in half by drawing a line segment from one vertex to its opposite vertex. This will create two triangles. Now use the congruences to prove that the opposite angles are congruent as well. When you are done, redraw the same quadrilateral but divide in half through the other vertices.