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Ch. 1 - Angles and the Trigonometric Functions
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601당신이 사용하는 게 아니라요?교과서 변경
1장, 문제 1.3.75

In Exercises 61–86, use reference angles to find the exact value of each expression. Do not use a calculator. tan(-𝜋/4)

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Recall that the tangent function is periodic and odd, meaning that \(\tan(-\theta) = -\tan(\theta)\). This property will help simplify \(\tan(-\pi/4)\).
Identify the reference angle for \(-\pi/4\). Since the angle is negative, its reference angle is the positive acute angle \(\pi/4\).
Find the value of \(\tan(\pi/4)\). From the unit circle or special triangles, \(\tan(\pi/4) = 1\).
Apply the odd function property: \(\tan(-\pi/4) = -\tan(\pi/4) = -1\).
Thus, the exact value of \(\tan(-\pi/4)\) is \(-1\).

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주요 개념

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

Reference Angles

A reference angle is the acute angle formed between the terminal side of an angle and the x-axis. It helps simplify trigonometric calculations by relating any angle to a corresponding angle in the first quadrant, where trigonometric values are well-known.
추천 영상:
5:31
Reference Angles on the Unit Circle

Tangent Function and Its Properties

The tangent of an angle in the unit circle is the ratio of the sine to the cosine of that angle. It is periodic with period π and odd, meaning tan(-θ) = -tan(θ), which is useful for evaluating tangent of negative angles without a calculator.
추천 영상:
5:43
Introduction to Tangent Graph

Exact Values of Special Angles

Certain angles like π/4, π/3, and π/6 have known exact trigonometric values. For π/4, tan(π/4) = 1, so using these exact values avoids approximation and calculator use, enabling precise answers for trigonometric expressions.
추천 영상:
04:39
45-45-90 Triangles