Question

What is the amplitude and period of `y=-4cos2x`?

Answer 1

`4,pi`

Explanation:

`"the standard form of the cosine is"`

`color(red)(bar(ul(|color(white)(2/2)color(black)(y=acos(bx+c)+d)color(white)(2/2)|)))`

`"amplitude "=|a|," period "=(2pi)/b`

`"phase shift "=-c/b," vertical shift "=d`

`"here "a=-4,b=2,c=d=0`

`rArr"amplitude "=|-4|=4," period "=(2pi)/2=pi`