Question

Which is an equation of the cosine function that has a period of π5
?(1 point)
Responses

f(x)=cosx

f left parenthesis x right parenthesis equals cosine x

f(x)=cos(10x)

f left parenthesis x right parenthesis equals cosine left parenthesis 10 x right parenthesis

f(x)=cos(x5)

f left parenthesis x right parenthesis equals cosine left parenthesis Start Fraction x over 5 End Fraction right parenthesis

f(x)=cos(x10)

f left parenthesis x right parenthesis equals cosine left parenthesis Start Fraction x over 10 End Fraction right parenthesis

Answer 1

f(x) = cos(10x)

Reason: For f(x)=cos(bx) the period is 2π/|b|. Set 2π/|b| = π/5 ⇒ |b| = 10, so b = 10.