Menus > Measure Menu > Value of Point

Selection prerequisites: One or more points constructed on path objects, or one path object and one point not on the path

If the selection is a path and a point not on the path, you must hold the Shift key to enable the command.

This Measure menu command measures the selected point’s relative position on the path on which it is constructed. The measured value depends on the type of path.

If a path and a point not on the path are selected, the command measures the value of the location on the path that’s closest to the selected point.

For some path objects, including axes, function plots, and parametric loci, the value of a point is determined explicitly by the numbering of the axis or by the value of the parameter. For other path objects, the value of a point is determined relative to the defining points of the path. For instance, points on segments, rays, lines, or arcs are measured relative to the two defining points, which are assigned values of 0 and 1. Points on closed paths (including circles and interiors) are measured relative to a defined starting point that is assigned a value of 0; these values go from 0 up to (but not including) 1.

Object	Possible Values
Segment	0 ≤ t ≤ 1
Ray	0 ≤ t
Line or Axis	all real numbers
Circle	0 ≤ t < 1
Arc	0 ≤ t ≤ 1
Interior (Circle Interior, Polygon, or Arc Interior)	0 ≤ t < 1
Point Locus defined by a point driver	0 ≤ t ≤ 1
Point Locus defined by a parameter driver	domain of driving parameter
Function Plot	domain of independent variable

Subtopic:

How to Construct a Slider