Problem:
In trapezoid the sides and are parallel, and the angles and are acute. Prove that it is possible to divide triangle into 4 disjoint triangles and triangle into 4 disjoint triangles such that the triangles and are congruent for every .
Problem:
In trapezoid the sides and are parallel, and the angles and are acute. Prove that it is possible to divide triangle into 4 disjoint triangles and triangle into 4 disjoint triangles such that the triangles and are congruent for every .
Solution:
Let be the reflection of with respect to , and let be the intersection of line with line . Since the angles are acute, lies inside segment . Moreover, since and are equidistant from , we have .
Through draw the lines and , and denote by the intersection of with , and by the intersection of with ; by construction we get
Similarly, through draw the lines and , and denote by the intersection of with , and by the intersection of with ; we get
Finally, let be the reflections of with respect to , and the choice
verifies the claim.