1
QuizMultiple Choice

Graphing Sine and Cosine Functions — Quiz

Question 1 • Precalculus

Which statement illustrates why cosine is an even function?

Answer
A
cosine of open paren pi over 4 close paren is equal to negative cosine times open paren 4 pi over 4 close paren
B
cosine of open paren negative pi over 4 close paren is equal to cosine of open paren pi over 4 close paren
C
cosine of open paren pi over 4 close paren is equal to negative cosine times open paren 5 pi over 4 close paren
D
cosine of open paren the fraction with numerator negative 7 pi and denominator 6 close paren is equal to cosine of open paren 5 pi over 4 close paren

Explanation

An even function satisfies f(-x) = f(x). For cosine, this means cos(-x) = cos(x), so cos(-π/4) = cos(π/4). Choice B states this property directly.

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