I am starting to think I have a fundamental misunderstanding of how sin() works.

e.g. the following code (just lines 12 and 14 are of interest here)

1. float XsinVal, angle, frequency = PI;
2. int XequiPos = 100; //the x-coordinate of the equilibrium position
3. int YequiPos = 100; //the y-coordinate of the oscillation
4. int amplitude = 50;
5. void setup() {
6.   size (300, 300);
7. }
8. void draw() {
9.   background (127);
10.   stroke(0);
11.   fill(0);                      
12.   XsinVal = sin(radians(angle))*amplitude;
13.   ellipse(XequiPos + XsinVal, YequiPos, 3, 3);
14.   angle -= frequency;
15. }

The first time through the draw() function, the angle is, I think 0 so sin(0)*amplitude = 0*50 = 0

Next time through and the angle is now -PI so sin(-PI)*amplitude = 0*50 = 0

And the angle becomes -2*PI and so sin(-2*PI)*amplitude = 0*50 = 0

and so on....

But how does this allow for the other value? It seems to me that the code should only give values of 0.

Thanks,

Shane