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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 2, Problem 28

The measures of two angles of a triangle are given. Find the measure of the third angle. See Example 2.
29.6° , 49.7°

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1
Recall that the sum of the interior angles of any triangle is always 180 degrees. This is a fundamental property of triangles.
Identify the given angles: the first angle is 29.6° and the second angle is 49.7°.
Set up an equation to find the third angle, which we can call \( x \):
\[ 29.6 + 49.7 + x = 180 \]
Combine the known angles on the left side:
\[ 79.3 + x = 180 \]
Solve for \( x \) by subtracting 79.3 from both sides:
\[ x = 180 - 79.3 \]

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Key Concepts

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

Triangle Angle Sum Property

The sum of the interior angles of any triangle is always 180 degrees. This fundamental property allows us to find the measure of an unknown angle when the other two angles are known by subtracting their sum from 180°.
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Sum and Difference of Tangent

Basic Arithmetic Operations

Solving for the unknown angle requires simple arithmetic, specifically addition and subtraction. Adding the two given angles and subtracting their sum from 180° yields the measure of the third angle.
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Algebraic Operations on Vectors

Angle Measurement Units

Angles are measured in degrees (°), a unit that divides a full rotation into 360 parts. Understanding this unit is essential for interpreting the given angle measures and performing calculations accurately.
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