Question

which cosine function has maximum of 4, a minimum of -4, and a period of 2pie/3?

Answer 1

@dan815 @hartnn @idku

Answer 2

period of cos x is 2π
period of cos (ax) is 2π/a because
cos (a(x + 2π/a) ) = cos (ax + 2π) = cos (ax)
if we need period 2π/3 the function must be cos (3x)

furthermore, as
- 1 ≤ cos x ≤ 1

it will be
- 2 ≤ 2 cos x ≤ 2

putting together the two things, the answer is c)
y = 2 cos (3θ)

Answer 3

de nada (¬‿¬)