Table of contents

0. Review of College Algebra4h 43m
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

1. Measuring Angles

Angles in Standard Position

Trigonometry

1. Measuring Angles

Angles in Standard Position

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1:22 minutes

Problem 52

Textbook Question

Use a calculator to determine whether each statement is true or false. A true statement may lead to results that differ in the last decimal place due to rounding error. cos 40° = 2 cos 20°

Verified step by step guidance

Convert the angles from degrees to radians if your calculator is in radian mode. Use the conversion: radians = degrees × (π/180).

Calculate \( \cos 40^\circ \) using a calculator.

Calculate \( \cos 20^\circ \) using a calculator.

Multiply the result of \( \cos 20^\circ \) by 2.

Compare the value of \( \cos 40^\circ \) with the result from the previous step to determine if the statement is true or false.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cosine Function

The cosine function is a fundamental trigonometric function that relates the angle of a right triangle to the ratio of the length of the adjacent side to the hypotenuse. It is defined for all angles and is periodic, with a range of values between -1 and 1. Understanding the properties of the cosine function is essential for evaluating expressions involving cosine, such as cos(40°) and cos(20°).

Trigonometric Identities

Trigonometric identities are equations that involve trigonometric functions and are true for all values of the variables involved. One important identity is the double angle formula for cosine, which states that cos(2θ) = 2cos²(θ) - 1. Recognizing and applying these identities can help simplify expressions and verify the truth of statements involving trigonometric functions.

Rounding Errors

Rounding errors occur when numerical values are approximated to a certain number of decimal places, which can lead to discrepancies in calculations. In trigonometry, using a calculator to evaluate functions can introduce rounding errors, especially when comparing values that are very close together. Understanding how rounding affects results is crucial for interpreting the accuracy of trigonometric calculations.