In △ A B C , ∠ A is 3 0 ∘ and ∠ B is 8 0 ∘ . What is the measure of the complement of ∠ C in degrees?
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"The compliment" is not frequently used.
Indeed but you learn something new every day
How is this a "Level 3" problem? Isn't some levelheadedness required here?
\[\begin{align} \angle A + \angle B + \angle C &= 180^{\circ} \\ (30^{\circ}) + (80^{\circ}) + \angle C &= 180^{\circ} \\ \angle C &= 70^{\circ} \implies \color{Blue}{[90 - 70 = \boxed{20}]}
\end{align}\]
∠ A C B = 1 8 0 − 8 0 − 3 0 = 7 0
The sum of complimentary angles is 9 0 ∘ . So the complement of ∠ A C B is 9 0 − 7 0 = 2 0
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Let the measure of ∠ C be x . We know that the sum of a triangle's angles is 1 8 0 ∘ . We also know that the first two angles sum up to 1 1 0 ∘ . From this, the measure of ∠ C is 1 8 0 ∘ − 1 1 0 ∘ = 7 0 ∘ . The complement of an angle is 9 0 − z , where z is the measure of the angle in degrees. Thus, the complement of ∠ C is 9 0 ∘ − 7 0 ∘ = 2 0 ∘ .