Ch. 2 - Acute Angles and Right Triangles

Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook

Lial 12th Edition

Ch. 2 - Acute Angles and Right Triangles

Problem 49

Chapter 3, Problem 49

Give the exact value of each expression. See Example 5. tan 30°

Verified step by step guidance

Recall the definition of the tangent function in terms of sine and cosine: \(\tan \theta = \frac{\sin \theta}{\cos \theta}\).

Identify the values of \(\sin 30^\circ\) and \(\cos 30^\circ\) using known special angles: \(\sin 30^\circ = \frac{1}{2}\) and \(\cos 30^\circ = \frac{\sqrt{3}}{2}\).

Substitute these values into the tangent formula: \(\tan 30^\circ = \frac{\frac{1}{2}}{\frac{\sqrt{3}}{2}}\).

Simplify the complex fraction by multiplying numerator and denominator appropriately: \(\tan 30^\circ = \frac{1}{2} \times \frac{2}{\sqrt{3}}\).

Further simplify the expression to get the exact value of \(\tan 30^\circ\) in simplest radical form.

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Key Concepts

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

Definition of the Tangent Function

The tangent of an angle in a right triangle is the ratio of the length of the opposite side to the adjacent side. It can also be expressed as tan(θ) = sin(θ)/cos(θ), linking it to the sine and cosine functions.

Special Angles and Their Exact Values

Certain angles like 30°, 45°, and 60° have well-known exact trigonometric values derived from special triangles. For 30°, these values come from the 30°-60°-90° triangle, enabling precise calculation without a calculator.

Using the 30°-60°-90° Triangle

The 30°-60°-90° triangle has side ratios of 1:√3:2. Knowing these ratios allows direct computation of trigonometric functions for 30°, such as tan 30° = opposite/adjacent = 1/√3, which can be rationalized to √3/3.

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30-60-90 Triangles

Related Practice

Textbook Question

Evaluate each expression. See Example 4. cot² 135° - sin 30° + 4 tan 45°

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Textbook Question

Give the exact value of each expression. See Example 5. sin 30°

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Determine whether each statement is true or false. See Example 4. csc 20° < csc 30°

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Textbook Question

Solve each problem. See Examples 1–4. Altitude of a Triangle Find the altitude of an isosceles triangle having base 184.2 cm if the angle opposite the base is 68°44'.

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