Question

What is the period and amplitude for `f(x)=3cos2x`?

Answer 1

You can "read" these information from your function:
1] The number multiplying the `cos` represents the AMPLITUE. So your `cos` oscillates between `+3` and `-3`;
2] The number multiplying the `x` in the argument allows you to evaluate the PERIOD as: `(period)=(2pi)/color(red)(2)=pi`. This means that your function needs the length `pi` to complete one oscillation. graph{3cos(2x) [-10, 10, -5, 5]}