Question

How do you find the amplitude and period of `y=2cosx`?

Answer 1

The amplitude is `<-2;2>` the period is `2pi`.

The basic amplitude of a cosine is `<-1;1>`, if you multiply the function by a number the amplitude of a function is also multiplied, so the amplitude of `y=2cosx` is `<-2;2>`.

The basic period of a cosine is `2pi` and it would change if there was a coefficient in front of `x` in a formula of the function.
In this case there are no coeficients, so the period remains unchanged.