# The amplitude of a sine graph

• April 21st 2009, 03:34 PM
tiar
The amplitude of a sine graph
Hi, I'm just going through a practice exam and looking over my answers compared to the answer key.

$y=3sin(x+\frac{\pi}{3}) - 1$

It asked for the range of the function in interval notation.
I put down [-1, 2], because I figured the amplitude was 3?

But the answer is [-4, 2]

I need some clarification as to why. Am I missing something? Do I multiply the amplitude by 2 or something weird?

• April 21st 2009, 03:57 PM
TheEmptySet
Quote:

Originally Posted by tiar
Hi, I'm just going through a practice exam and looking over my answers compared to the answer key.

$y=3sin(x+\frac{\pi}{3}) - 1$

It asked for the range of the function in interval notation.
I put down [-1, 2], because I figured the amplitude was 3?

But the answer is [-4, 2]

I need some clarification as to why. Am I missing something? Do I multiply the amplitude by 2 or something weird?

Remember that the sine function goes both up and down.

Here is a graph I hope it clears it up

Attachment 11033
• April 21st 2009, 04:13 PM
tiar
Quote:

Originally Posted by TheEmptySet
Remember that the sine function goes both up and down.

Here is a graph I hope it clears it up

Attachment 11033

OH! So the amplitude is between [-3, 3] but because of our shift down it's [-4, 2].

HAHA okay, thanks so much!!!!! :)