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iphoneobjective-cioscgpointpolar-coordinates

Objective-C rectangular CGPoint to polar CGPoint

I found the equations to convert an X,Y into radius and angle:

x = r*Cos(Q)
y = r*Sin(Q)

r= sqrt(x*x + y*y)
Q = tan^-1(y/x)

My problem is that I dont remember what is the syntax for the tan^-1 in objective C. I do not want to get things wrong.

This got me thinking: Why build this from scratch? Is there a built-in way to convert a given CGPoint in Objective C from polar to rectangular coordinates? Maybe there's some CAAnimation class that can help me with this?

Solution

  • To get the angle use:

    Q = atan2( y, x );

    This function will work out the quadrant to give the correct sign of the angle.