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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 10

CONCEPT PREVIEW Determine whether each statement is possible or impossible. sin² θ + cos² θ = 2

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1
Recall the Pythagorean identity in trigonometry, which states that for any angle \( \theta \), the following equation holds: \[ \sin^{2} \theta + \cos^{2} \theta = 1 \]
Understand that \( \sin^{2} \theta \) means \( (\sin \theta)^{2} \) and similarly for \( \cos^{2} \theta \). Both sine and cosine values range between -1 and 1, so their squares range between 0 and 1.
Since both \( \sin^{2} \theta \) and \( \cos^{2} \theta \) are non-negative and their sum is always exactly 1, check if the given statement \( \sin^{2} \theta + \cos^{2} \theta = 2 \) can ever be true.
Consider the maximum possible values of \( \sin^{2} \theta \) and \( \cos^{2} \theta \). The maximum value for each is 1, but since they are complementary in the identity, their sum cannot exceed 1.
Conclude that the statement \( \sin^{2} \theta + \cos^{2} \theta = 2 \) is impossible because it contradicts the fundamental Pythagorean identity.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
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주요 개념

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

Pythagorean Identity

The Pythagorean identity states that for any angle θ, sin²θ + cos²θ = 1. This fundamental trigonometric identity is derived from the Pythagorean theorem and holds true for all real values of θ.
추천 영상:
6:25
Pythagorean Identities

Range of Sine and Cosine Functions

The sine and cosine functions each have values ranging between -1 and 1. Consequently, their squares, sin²θ and cos²θ, range from 0 to 1, which restricts the possible sums of these squares.
추천 영상:
5:53
Graph of Sine and Cosine Function

Evaluating the Possibility of a Statement

To determine if a trigonometric statement is possible, compare it against known identities and function ranges. Since sin²θ + cos²θ always equals 1, the statement sin²θ + cos²θ = 2 is impossible.
추천 영상:
7:28
Evaluate Composite Functions - Values Not on Unit Circle