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Ch. 2 - Acute Angles and Right Triangles
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
3장, 문제 10

Determine whether each statement is true or false. If false, tell why. csc 22° ≤ csc 68°

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Recall the definition of the cosecant function: \(\csc \theta = \frac{1}{\sin \theta}\). This means that the value of \(\csc \theta\) depends inversely on \(\sin \theta\).
Since \(\sin \theta\) is positive in the first quadrant (where both 22° and 68° lie), compare \(\sin 22^\circ\) and \(\sin 68^\circ\) to understand the behavior of their cosecants.
Note that \(\sin 22^\circ\) is less than \(\sin 68^\circ\) because sine increases from 0° to 90°, so \(\sin 22^\circ < \sin 68^\circ\).
Because \(\csc \theta = \frac{1}{\sin \theta}\), a smaller sine value corresponds to a larger cosecant value. Therefore, \(\csc 22^\circ > \csc 68^\circ\).
Conclude that the statement \(\csc 22^\circ \leq \csc 68^\circ\) is false, since \(\csc 22^\circ\) is actually greater than \(\csc 68^\circ\).

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주요 개념

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

Definition and Properties of the Cosecant Function

The cosecant function, csc(θ), is the reciprocal of the sine function, defined as csc(θ) = 1/sin(θ). It is important to understand that csc(θ) is undefined when sin(θ) = 0 and that its values depend inversely on the sine values.
추천 영상:
6:22
Graphs of Secant and Cosecant Functions

Behavior of the Sine Function in the First Quadrant

In the first quadrant (0° to 90°), the sine function increases as the angle increases. Therefore, sin(22°) < sin(68°), which directly affects the values of their reciprocals, the cosecants.
추천 영상:
5:53
Graph of Sine and Cosine Function

Inequality Relations Involving Reciprocal Functions

When comparing reciprocal functions like cosecant, the inequality reverses relative to the sine values. Since csc(θ) = 1/sin(θ), if sin(22°) < sin(68°), then csc(22°) > csc(68°), which is crucial for determining the truth of the given inequality.
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Introduction to Relations and Functions
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