Proof
1: AC = RT - correosponding sides in congruent triangles ( ) are equal
2: - correosponding angles in congruent triangles () are equal
3: - Given (Altitudes CD to AB and TV to RS)
4: - From 1,2,3 AAS - If two angles and a nonincluded side of one triangle are congruent to two angles and a nonincluded side of a second triangle, then the triangles are congruent (AAS)
5: CD = TV - CPCTC - Congruent Parts Congruent Triangles Congruent