|Syntax||PTR_X (argument, module)|
The function PTR_X transforms a point (described in polar co-ordinates) into the rectangular co-ordinates and returns the real part of the latter. argument is an angle in radians, module a radius.
A line in rectangular co-ordinates transformed to polar co-ordinates looks like a circle when plotted on screen. However, if you were to look at this line using polar co-ordinates, it would appear as straight line again. Confused?
100 SCALE 10,-5,-5: PAPER 0: CLS 110 FOR a = 0 TO 2*PI STEP PI/128 120 POINT PTR_X(a,2), PTR_Y(a,2) 130 END FOR a