Table of contents
- 0. Review of College Algebra4h 45m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
2. Trigonometric Functions on Right Triangles
Trigonometric Functions on Right Triangles
Problem 15
Textbook Question
Sketch an angle θ in standard position such that θ has the least positive measure, and the given point is on the terminal side of θ. Then find the values of the six trigonometric functions for each angle. Rationalize denominators when applicable. See Examples 1, 2, and 4. (―8 , 15)
Verified step by step guidance1
Step 1: Understand the problem. You are given a point (-8, 15) on the terminal side of an angle \( \theta \) in standard position. The goal is to sketch this angle and find the six trigonometric functions: sine, cosine, tangent, cosecant, secant, and cotangent for \( \theta \).
Step 2: Calculate the radius \( r \), which is the distance from the origin to the point \((-8, 15)\). Use the distance formula:
\[ r = \sqrt{x^2 + y^2} = \sqrt{(-8)^2 + 15^2} \]
Step 3: Find the six trigonometric functions using the definitions based on the coordinates and radius:
- \( \sin \theta = \frac{y}{r} \)
- \( \cos \theta = \frac{x}{r} \)
- \( \tan \theta = \frac{y}{x} \)
- \( \csc \theta = \frac{r}{y} \)
- \( \sec \theta = \frac{r}{x} \)
- \( \cot \theta = \frac{x}{y} \)
Step 4: Determine the quadrant of the angle \( \theta \). Since \( x = -8 \) (negative) and \( y = 15 \) (positive), the point lies in the second quadrant. This helps understand the signs of the trigonometric functions.
Step 5: Rationalize denominators if any of the trigonometric function values have radicals in the denominator, and express all six functions in simplest form with correct signs based on the quadrant.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Standard Position of an Angle
An angle is in standard position when its vertex is at the origin of the coordinate plane and its initial side lies along the positive x-axis. The terminal side is determined by rotating the initial side counterclockwise by the angle measure θ. Sketching the angle involves plotting the given point on the terminal side and drawing the angle accordingly.
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Finding the Reference Angle and Least Positive Angle
The least positive angle θ is the smallest positive rotation from the initial side to the terminal side that passes through the given point. To find θ, determine the quadrant of the point and calculate the angle using inverse trigonometric functions or the arctangent of y/x, adjusting for the correct quadrant to ensure the angle is positive and less than 360°.
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Six Trigonometric Functions from a Point on the Terminal Side
Given a point (x, y) on the terminal side, the six trigonometric functions—sine, cosine, tangent, cosecant, secant, and cotangent—can be found using the definitions: sin θ = y/r, cos θ = x/r, tan θ = y/x, where r = √(x² + y²). The reciprocal functions are cosecant = 1/sin θ, secant = 1/cos θ, and cotangent = 1/tan θ. Rationalizing denominators ensures simplified exact values.
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Related Practice
Textbook Question
If sin θ = a and cos θ = b, represent each of the following in terms of a and b.tan θ - sec θ
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