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Points
Points
Points are the fundamental building blocks
of classical geometry, and geometric figures such as lines and circles
are defined in terms of points. All of Sketchpad’s geometric constructions
begin with points.
Points in Sketchpad are of three kinds.
An independent point has no parents,
and so does not depend on any other object. An independent point is free
to move anywhere on the sketch plane.
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A point on path is constructed on a path object such as a line or circle.
A point on path is free to move along its path, but cannot leave that
path.
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A dependent point—such as a point of intersection—is constructed in such
a way that its position is completely determined by its parents. A dependent
point cannot move by itself. The point can move only if at least one of
its parent objects also moves. Thus, a point at the intersection of two
segments cannot move unless one or both of the intersecting segments are
moved, and the reflected
image of a point cannot move unless either the pre-image or the mirror
moves.
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Subtopics:
Moving and Animating Points
Splitting and Merging Points
Constructing Points
Using Points in Transformations
Measuring Points
See also
Object Relationships: Parents and Children
Point Tool
Selecting
and Deselecting Objects
Showing and Hiding Labels
Straightedge Tools
Compass Tool
Custom Tools
Path Objects
Point On Object
Intersection
Midpoint
Principles of Animation
Dragging Objects