Question

How do you find the period, amplitude and sketch `y=-3cos4x`?

Answer 1

When given an equation of the form: `y = Acos(Bx + C) + D`
Amplitude is : |A|
Period is: `T = (2pi)/B`
Phase shift is: `phi = -C/B`
Vertical shift is: D

Explanation:

For the given case `A = -3, B = 4, C = 0 and D = 0`

The amplitude is the absolute value of A, |-3| = 3

The period is:

`T = (2pi)/B`

`T = (2pi)/4`

`T = pi/2`