Question

8. Find the period and amplitude of the function.

Answer 1

The general equation of the cosine function is
y = a cos nθ
where a is the amplitude 
And n = 2π/period

by comparing the general equation with the given equation which is 
Y = 5 cos 2θ
∴ a = 5  and   n = 2
∴ period = 2π/n = 2π/2 = π
∴ The amplitude = 5   and  the period = π

So, the correct answer is the second option

Period pi, radians; amplitude: 5