# The y axis for the sine wave

Okay this has been bothering me, I know what the x axis on sine graph mean, but not the y axis. I know when I type for example: sin(pi) I will get 1. But what is that 1? I know its the y cordnate. But what is it?

SteamKing
Staff Emeritus
Homework Helper
It's the amplitude of the sine wave.

Since the sine function is related to a unit circle, think of the amplitude as the y coordinate on the unit circle when the radius makes an angle theta to the positive x-axis.

Sine(pi) equals zero. Geometrically the sine of angle α equals the length of the opposite side divided by the length of the hypotenuse in a right triangle. The particular size of the triangle is unrelevant as long as it contains the angle. In an unit circle centered at the origin sine(α) equals the distance of a point on the circumference (at angle α) from the x-axis. It corresponds to the imaginary part of e^(iα) in complex analysis.

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HallsofIvy
Homework Helper
Okay this has been bothering me, I know what the x axis on sine graph mean, but not the y axis. I know when I type for example: sin(pi) I will get 1. But what is that 1? I know its the y cordnate. But what is it?
I am wondering what you think the x axis "means" and what kind meaning you want the y axis to have. The only "meaning" the x axis in any graph has is the values of x, the independent variable. And the only "meaning" the y axis has is the value of y the function assigns to the corresponding x.

And, by the way, "sin(pi)" is 0, not 1.

Stephen Tashi