Inside Macintosh: QuickDraw GX Environment and Utilities /

Chapter 8 - QuickDraw GX Mathematics / Using QuickDraw GX Mathematics

Converting Between Cartesian and Polar Coordinates

You can use QuickDraw GX functions to convert between Cartesian and polar coordinates. The PolarToPoint function converts a point in polar coordinates to Cartesian coordinates, (r, a) to (x, y). The PointToPolar function converts a point in Cartesian coordinates to polar coordinates, (x, y) to (r, a). The gxPolar point (r, a) corresponds to the gxPoint point (r cos(a), r sin(a)). Since r2 = x2 + y2 and tan(a) = y / x, the gxPoint structure (100, 100) corresponds to the gxPolar structure (141.42136, 45). Figure 8-19 shows the Cartesian coordinate of point (100, 100) and the polar coordinate of identical point (141.42136, 45).

Figure 8-19 Converting between Cartesian and polar coordinates

The Cartesian and polar coordinate systems are described in the section "Cartesian and Polar Coordinate Conversion" beginning on page 8-10. The PolarToPoint function is described on page 8-56. The PointToPolar function is described on page 8-57.