A good answer might be:

The problem is that sin(x) has values from -1.0 up to 1.0. When these are changed to int type in the statement

int startY = (int)Math.sin( x );

they will almost always be zero.

Adjusting Values

To use the drawLine() method, the endpoints of the line need to be positive integers. But what we want to graph consists of negative and positive numbers smaller than one!

To deal with this problem you need to scale the computed values into graphics coordinates. Say that the applet is 600 pixels wide, and that this is supposed to represent the range of 0.0 to 2*PI. So we have:

actual x valueinteger X to fit applet width
0.0 0
2*PI 599

The floating point number x can be changed into the correct integer X by using a linear equation:

X = x * 599/(2*PI)

This may look awful, but it is just algebra.


Err... just algebra.... sure... Maybe we better check if it works. Fill in the following table by computing X by using the formula.

actual x valueX = x * 599/(2*PI)