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Ch. 2 - Graphs of the Trigonometric Functions; Inverse Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 83

In Exercises 83–94, use a right triangle to write each expression as an algebraic expression. Assume that x is positive and that the given inverse trigonometric function is defined for the expression in x. tan (cos⁻¹ x)

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1
Recognize that the expression \( \tan(\cos^{-1} x) \) involves the tangent of an angle whose cosine is \( x \). Let \( \theta = \cos^{-1} x \), so \( \cos \theta = x \).
Since \( \theta \) is an angle in a right triangle, draw a right triangle where the adjacent side to angle \( \theta \) is \( x \) and the hypotenuse is 1 (because cosine is adjacent over hypotenuse).
Use the Pythagorean theorem to find the length of the opposite side: \( \text{opposite} = \sqrt{1^2 - x^2} = \sqrt{1 - x^2} \).
Recall that \( \tan \theta = \frac{\text{opposite}}{\text{adjacent}} \). Substitute the values found: \( \tan(\cos^{-1} x) = \frac{\sqrt{1 - x^2}}{x} \).
Express the final algebraic expression for \( \tan(\cos^{-1} x) \) as \( \frac{\sqrt{1 - x^2}}{x} \), assuming \( x > 0 \) to keep the expression defined.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Inverse Trigonometric Functions

Inverse trigonometric functions, like cos⁻¹(x), return an angle whose trigonometric ratio equals x. Understanding how to interpret these functions is essential for converting expressions involving inverse trig functions into geometric or algebraic forms.
추천 영상:
4:28
Introduction to Inverse Trig Functions

Right Triangle Definitions of Trigonometric Ratios

Trigonometric ratios such as sine, cosine, and tangent can be represented as ratios of sides in a right triangle. Using a right triangle to represent an angle from an inverse trig function helps translate the problem into algebraic expressions involving side lengths.
추천 영상:
5:19
Solving Right Triangles with the Pythagorean Theorem

Pythagorean Theorem

The Pythagorean theorem relates the sides of a right triangle: a² + b² = c². It is crucial for finding missing side lengths when one side and an angle are known, enabling the expression of trigonometric ratios purely in terms of x.
추천 영상:
5:19
Solving Right Triangles with the Pythagorean Theorem