Aconjecture and the paragraph proof used to prove the conjecture are shown. given: r s t u is a parallelogram. angle 1 and angle 3 are complementary. prove: angle 2 and angle 3 are complementary. parallelogram j k l m. a diagonal segment u s is drawn across the parallelogram. angle r u s is labeled 1. angle u s t is labeled 2. a ray is extended diagonally up to the left of ut forming an interior angle labeled as 3.drag an expression or phrase to each box to complete the proof. it is given that rstu is a parallelogram, so ru¯¯¯¯¯∥st¯¯¯¯¯ by the definition of parallelogram. therefore, ∠1≅∠2 by the alternate interior angles theorem, and m∠1=m∠2 by the blank . it is also given that ∠1 and ∠3 are complementary, so m∠1+m∠3=90° by the blank . by substitution, m∠2+ blank = 90°, and so ∠2 and blank are complementary by the definition of complementary. choices: definition of complementary, angle congruence postulate, < 1, < 3, m< 1, m< 3