radial-line-circle-intersection

Arguments: point circle-center radius &optional pos-to-return

Returns the point on the edge of a circle where it is crossed by a line that passes through the center of the circle and through an arbitrary point. Returns nil if the circle center and the arbitrary point are the same. The first argument is a position object for the arbitrary point. The second argument is a position object for the center of the circle, and the third argument is a real number for the radius of the circle. Returns a position object or nil.

If pos-to-return is nil or unspecified, then a new position object is created and returned. Otherwise pos-to-return should be a position object, which will be modified and returned.

As usual, position objects should contain integers. See make-position. See also radial-line-circle-intersection-x-y.

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This page is new in the 8.2 release.
Created 2016.6.21.