The proof that vertical angles 1 and 3 are congruent is started below. The image is of a parallelogram with longer horizontal diagonal. The vertically opposite angles marked at intersection of diagonals are 2, 4 and 1, 3 respectively Statement Reason m∠1 + m∠2 = 180° Angles 1 and 2 are supplementary angles. m∠2 + m∠3 = 180° Angles 2 and 3 are supplementary angles. Which statement might be next?

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