Syntax PTR_X (argument, module)
Location PTRRTP

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


The other rectangular co-ordinate is found with PTR_Y below. Also see RTP_R and RTP_T