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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 35

An equation of the terminal side of an angle θ in standard position is given with a restriction on x. Sketch the least positive such angle θ , and find the values of the six trigonometric functions of θ . 12x + 5y = 0 , x ≥ 0 .

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1
Rewrite the given equation of the terminal side in slope-intercept form to understand the line better. Starting with \(12x + 5y = 0\), solve for \(y\) to get \(y = -\frac{12}{5}x\).
Recognize that the terminal side of angle \(\theta\) lies along the line \(y = -\frac{12}{5}x\) with the restriction \(x \geq 0\). This means the terminal side is in the fourth quadrant or on the positive x-axis.
Find the reference angle \(\alpha\) by considering the slope as the tangent of the angle the line makes with the positive x-axis. Use \(\tan(\alpha) = \left| -\frac{12}{5} \right| = \frac{12}{5}\), then find \(\alpha = \arctan\left(\frac{12}{5}\right)\).
Determine the least positive angle \(\theta\) in standard position. Since the line is in the fourth quadrant (because \(x \geq 0\) and \(y\) is negative), calculate \(\theta = 2\pi - \alpha\) (in radians) or \(360^\circ - \alpha\) (in degrees).
Calculate the six trigonometric functions of \(\theta\) by first choosing a point on the terminal side that satisfies the line equation and \(x \geq 0\). For example, use \(x = 5\), then \(y = -12\). Compute the hypotenuse \(r = \sqrt{x^2 + y^2} = \sqrt{5^2 + (-12)^2}\). Then use the definitions: \(\sin \theta = \frac{y}{r}\), \(\cos \theta = \frac{x}{r}\), \(\tan \theta = \frac{y}{x}\), \(\csc \theta = \frac{r}{y}\), \(\sec \theta = \frac{r}{x}\), and \(\cot \theta = \frac{x}{y}\).

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주요 개념

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

Standard Position of an Angle

An angle in standard position has its vertex at the origin and its initial side along the positive x-axis. The terminal side is determined by rotating the initial side by the angle θ. Understanding this helps in visualizing and sketching the angle based on the given line equation.
추천 영상:
05:50
Drawing Angles in Standard Position

Equation of a Line and Its Relation to an Angle

The equation 12x + 5y = 0 represents a line through the origin. The slope of this line corresponds to the tangent of the angle θ formed by the terminal side with the positive x-axis. The restriction x ≥ 0 limits the terminal side to the right half-plane, ensuring the angle is the least positive angle.
추천 영상:
04:47
Introduction to Parametric Equations

Six Trigonometric Functions

The six trigonometric functions—sine, cosine, tangent, cosecant, secant, and cotangent—are ratios of the sides of a right triangle or coordinates on the unit circle. Once θ is identified, these functions can be calculated using the coordinates of a point on the terminal side or the slope of the line.
추천 영상:
6:04
Introduction to Trigonometric Functions