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left:
top:
The formula used for this cosine wave is:

     left(t) = t * 10 + xcenter
     top(t) = stretch * sin(t/divisor) + ycenter

Left is the number of pixels from the left of the screen and top is the number of pixels from the top of the screen. Stretch is 40 and divisor is 2. The range of t is [0,6.5π]. the step of t is 0.1.

I got this formula from my head.

The behavior of this function is inexplicable. I don't know why it accelerates and decelerates, but it does.