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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 79

Give all six trigonometric function values for each angle θ. Rationalize denominators when applicable. See Examples 5–7.
sin θ = √2/6 , and cos θ < 0

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1
Identify the given information: \(\sin \theta = \frac{\sqrt{2}}{6}\) and \(\cos \theta < 0\). This tells us the sine value and that the cosine is negative, which helps determine the quadrant of \(\theta\).
Recall the Pythagorean identity: \(\sin^2 \theta + \cos^2 \theta = 1\). Use this to find \(\cos \theta\) by substituting the given sine value: \(\left(\frac{\sqrt{2}}{6}\right)^2 + \cos^2 \theta = 1\).
Calculate \(\cos^2 \theta\) from the equation and then take the square root to find \(\cos \theta\). Since \(\cos \theta < 0\), choose the negative root.
Find \(\tan \theta\) using the definition \(\tan \theta = \frac{\sin \theta}{\cos \theta}\). Substitute the values found for sine and cosine.
Calculate the reciprocal functions: \(\csc \theta = \frac{1}{\sin \theta}\), \(\sec \theta = \frac{1}{\cos \theta}\), and \(\cot \theta = \frac{1}{\tan \theta}\). Rationalize denominators where necessary.

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주요 개념

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

Definition of the Six Trigonometric Functions

The six trigonometric functions—sine, cosine, tangent, cosecant, secant, and cotangent—are ratios of sides in a right triangle or coordinates on the unit circle. Given sin θ, the other functions can be found using their relationships, such as tan θ = sin θ / cos θ and reciprocal identities like csc θ = 1 / sin θ.
추천 영상:
6:04
Introduction to Trigonometric Functions

Using the Pythagorean Identity to Find Missing Values

The Pythagorean identity, sin²θ + cos²θ = 1, allows calculation of an unknown trigonometric value when one is given. Here, knowing sin θ and the sign of cos θ helps determine cos θ accurately, which is essential for finding all six function values.
추천 영상:
6:25
Pythagorean Identities

Sign Determination Based on Quadrants

The sign of trigonometric functions depends on the quadrant where angle θ lies. Since sin θ is positive and cos θ is negative, θ is in the second quadrant. This information guides the correct sign assignment for all six functions, ensuring accurate results.
추천 영상:
6:36
Quadratic Formula