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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 2, Problem 17

Find all unknown angle measures in each pair of similar triangles.

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1
Recall that in similar triangles, corresponding angles are congruent, meaning they have the same measure.
Identify the pairs of corresponding angles between the two triangles based on their given information or markings.
Set the measures of the corresponding angles equal to each other to form equations.
Use the fact that the sum of the interior angles in any triangle is \(180^\circ\), so for each triangle, write the equation \(A + B + C = 180^\circ\) where \(A\), \(B\), and \(C\) are the angles of the triangle.
Solve the system of equations formed by the equal angles and the triangle angle sum to find the unknown angle measures.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Similarity of Triangles

Two triangles are similar if their corresponding angles are equal and their corresponding sides are proportional. This means that the shape is the same, but the size may differ. Recognizing similarity allows us to relate unknown angles and sides between triangles.
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Corresponding Angles in Similar Triangles

In similar triangles, each angle in one triangle matches exactly one angle in the other triangle. Knowing one angle in a pair helps find the corresponding unknown angle in the other triangle, since corresponding angles are congruent.
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Angle Sum Property of Triangles

The sum of the interior angles in any triangle is always 180 degrees. This property helps find unknown angles when some angles are known, by subtracting the sum of known angles from 180 degrees.
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Sum and Difference of Tangent