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°

Key Concepts

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.