Why does my child think y = 3 sin x has an amplitude of 6?
Your child gives the whole height of a wave, top to bottom, as its amplitude, such as 6 instead of 3 for y = 3 sin x.
Why children do it
The wave goes from −3 to 3, a height of 6, and that's what children measure. But the amplitude is measured from the middle line, the x-axis here, up to the top: 3, the number in front of sin x.
How to help at home
Ask them to measure from the middle line up to the top, not from the bottom.
The right way
This is the graph of y = k sin x. What is k?
- 3The wave rises to 3 above the middle, so k = 3.
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