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Ch. 2 - Acute Angles and Right Triangles
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 3, Problema 13

Suppose ABC is a right triangle with sides of lengths a, b, and c and right angle at C. Use the Pythagorean theorem to find the unknown side length. Then find exact values of the six trigonometric functions for angle B. Rationalize denominators when applicable. See Example 1. a = 6, c = 7

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Identify the sides of the right triangle ABC, where the right angle is at C. This means side c is the hypotenuse, and sides a and b are the legs adjacent to angle C. Given a = 6 and c = 7, we need to find side b using the Pythagorean theorem.
Apply the Pythagorean theorem: \(a^2 + b^2 = c^2\). Substitute the known values: \(6^2 + b^2 = 7^2\).
Simplify the equation: \(36 + b^2 = 49\). Then solve for \(b^2\) by subtracting 36 from both sides: \(b^2 = 49 - 36\).
Calculate \(b\) by taking the square root of both sides: \(b = \sqrt{13}\). This gives the exact length of side b.
Next, find the six trigonometric functions for angle B. Recall that angle B is opposite side b, adjacent to side a, and the hypotenuse is c. Use the definitions: \(\sin B = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{b}{c}\), \(\cos B = \frac{a}{c}\), \(\tan B = \frac{b}{a}\), and their reciprocals \(\csc B = \frac{c}{b}\), \(\sec B = \frac{c}{a}\), \(\cot B = \frac{a}{b}\). Substitute the known values and rationalize denominators where necessary.

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Pythagorean Theorem

The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (side opposite the right angle) equals the sum of the squares of the other two sides. It is expressed as c² = a² + b². This theorem allows you to find an unknown side length when the other two are known.
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Solving Right Triangles with the Pythagorean Theorem

Trigonometric Functions in Right Triangles

The six trigonometric functions—sine, cosine, tangent, cosecant, secant, and cotangent—relate the angles of a right triangle to the ratios of its sides. For an angle, sine is opposite/hypotenuse, cosine is adjacent/hypotenuse, and tangent is opposite/adjacent. The reciprocal functions are cosecant, secant, and cotangent.
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Rationalizing Denominators

Rationalizing the denominator involves eliminating any square roots or irrational numbers from the denominator of a fraction. This is done by multiplying numerator and denominator by a suitable radical expression. It is a standard practice to present trigonometric values in simplified, exact form.
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