1. Angles of Triangles
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Focus on the leftmost triangle in the figure.
26^(∘)
Let's highlight ∠3, which we are asked to find. We will focus on the triangle that has it as one of its angles. Notice that the measure of one interior and exterior angle of this triangle is given on the figure.
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Exterior Angle Theorem |
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The measure of the exterior angle is the sum of the measures of the two remote interior angles. |
This theorem lets us set up and solve an equation for m∠3. 25^(∘) +m∠3=51^(∘) → m∠3 =26^(∘)
interiorof the angle, and
exteriorof the angle.
These regions can be examined in the following graph.
Notice that the interior of an angle is the region for which the angle measure is less than 180^(∘).