CPM Homework Help : GC Problem 9-71

Rectangle A B C D, where side D C, is missing, with segments from, D to B, & from, A to C, side A D & side B C, each have 2 tick marks, angle D A B, & angle C B A, each have right angle mark. Given the information in the diagram at right, prove that $∠C ≅ ∠D$ . Write your proof using any format studied so far.

Step 1:

Proof with 2 bubbles: bubble #1: D A, = C B, given, bubble #2: Angle, D A B, & angle, C B A is each a right angle, given.

Step 2:

Added to Proof: bubble #3: angle, D A B, congruent to angle, C B A, all right angles are congruent, arrow from bubble #2 to #3.

Step 3:

Added to proof: bubble #4, A B, = B A, reflexive property.

Step 4:

Added to Proof: bubble #5, bubbles # 1, # 3, & # 4 each have an arrow pointing to bubble # 5: Triangle, D A B, is congruent to triangle, C B A, S A S, congruency.

Step 5:

Added to Proof: bubble #6, & arrow from bubble # 5 to bubble #6: Angle, C is congruent to angle, D, congruent triangles have congruent parts.