Answers:
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Angle B: 81° .
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Angle C: 99° .
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Angle D: 81° .
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Explanation:
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Angle B:
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Given: m∡A = 99° ;
∡A and ∡B are "supplementary angles" ;
and supplementary angles add up to 180°.
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→ So, m∡B = 180 − 99 = 81° .
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Angle C: 99° .
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Explanation:
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Given: m∡A = 99° .
∡A and ∡C are "vertical angles". Vertical angles are congruent.
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→ So m∡A = m∡C = 99° .
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Angle D: 81° .
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Explanation:
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∡B and ∡D are vertical angles. Vertical angles are congruent.
As previously determined above, m∡B = 81° .
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→ So, m∡D = m∡B = 81° .
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