SOLUTION: If angles 1 and 2 are supplementary, and angle 1 is obtuse, prove angle 2 is acute.

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Question 811964: If angles 1 and 2 are supplementary, and angle 1 is obtuse, prove angle 2 is acute.
Answer by solver91311(24713) About Me  (Show Source):
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Measure angle 1 plus measure angle 2 = 180 by definition of supplementary.

Measure angle 1 greater than 90 by definition of obtuse.

Measure angle 2 = 180 minus measure angle 1 by addition postulate

If measure angle 1 is greater than 90, then measure angle 1 must be equal to 90 plus some real number x where x is greater than zero. Definition of "greater than"

Measure angle 2 = 180 - (90 + x) = 90 - x where x > 0. By substitution and the distributive property.

Measure angle 2 is less than 90 by definition of "less than"

Angle 2 is acute by definition of acute.

John

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