A conjecture and the paragraph proof used to prove the conjecture are shown. Given: ABCD is a parallelogram. Segment DC bisects angle B D E. Prove: angle 1 is congruent to angle 3. Parallelogram A B C D. Two rays D B and D E share endpoints at vertex D. Ray D B extends diagonally up to the right from D C at vertex D forming interior angles A B D and B D C. Angle A B D is labeled 1 and angle B D C is labeled 2. Ray D E extends diagonally down to the right from segment D C at vertex D forming an exterior angle C D E. Angle C D E is labeled 3.

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