Work out the y-coordinates of the points that are being drawn:
50 * sin((-175/100) * 2π)
50 * sin((-174/100) * 2π)
50 * sin((-173/100) * 2π)
...
50 * sin((175/100) * 2π)
50 * sin((176/100) * 2π)
The 50 simply scales things up because sin
values are between 0 and 1, so multiplying by 50 means the y-coordinates go from -50 to 50, enabling you to see the graph much better.
The arguments to the sin function are similarly scaled to go from -3.5π to 3.5π because the author of this script thought that would be a good range for the x-axis. And note the code is making 350 steps as it goes from left to right.
Bottom line is that this code was thought by its author to "look good".