Spherical Coordinate System

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XY Angle: The angle from Point 1 to Point 2 relative to the XY Plane. In other words, if the XY plane were a projector screen, and the front view of the drawing was projected on to that screen, the angle would be measured from Point 1 to Point 2 on the screen.

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Z Angle: The angle from the Z-Axis to the second point.

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