Concept Check Suppose that 90° < θ < 180° . Find the sign of each function value. cos ( ―θ)
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 105
Textbook Question
Concept Check Find a solution for each equation. tan (3θ ― 4°) = 1 / [cot(5θ ― 8°)]
Verified step by step guidance1
Recall the identity relating tangent and cotangent: \(\tan x = \frac{1}{\cot x}\). This means the equation \(\tan(3\theta - 4^\circ) = \frac{1}{\cot(5\theta - 8^\circ)}\) can be rewritten using this identity.
Rewrite the right side using the identity: \(\frac{1}{\cot(5\theta - 8^\circ)} = \tan(5\theta - 8^\circ)\). So the equation becomes \(\tan(3\theta - 4^\circ) = \tan(5\theta - 8^\circ)\).
Use the property that if \(\tan A = \tan B\), then \(A = B + k \times 180^\circ\), where \(k\) is any integer. Set up the equation: \(3\theta - 4^\circ = 5\theta - 8^\circ + k \times 180^\circ\).
Solve the equation for \(\theta\): Rearrange terms to isolate \(\theta\) on one side, which gives \(3\theta - 5\theta = -8^\circ + 4^\circ + k \times 180^\circ\), simplifying to \(-2\theta = -4^\circ + k \times 180^\circ\).
Divide both sides by \(-2\) to find \(\theta\): \(\theta = \frac{4^\circ - k \times 180^\circ}{2}\). This expression gives the general solution for \(\theta\) depending on integer values of \(k\).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Relationship Between Tangent and Cotangent
Tangent and cotangent are reciprocal trigonometric functions, meaning tan(x) = 1/cot(x) and cot(x) = 1/tan(x). Recognizing this relationship allows simplification of equations involving both functions by converting one into the other.
Recommended video:
Introduction to Cotangent Graph
Solving Trigonometric Equations
Solving trigonometric equations involves isolating the trigonometric function and finding all angle solutions within the domain. Since trigonometric functions are periodic, solutions often include general forms with added multiples of the function's period.
Recommended video:
How to Solve Linear Trigonometric Equations
Angle Manipulation and Equation Setup
Understanding how to manipulate angles inside trigonometric functions, such as linear expressions like 3θ - 4°, is essential. Setting up the equation correctly by equating angles or their trigonometric values helps in finding the variable θ.
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Parameterizing Equations
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