Line through a Point - Cinderella Documentation
Description: The user's guide to the Interactive Geometry Software Cinderella

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# Line through a Point

This mode creates a line through a point with a certain slope. When the point is moved, the slope of the line stays constant. However, in move mode it is also possible to select the line and change its slope. So this mode could also be called "line by slope." The mode generates the line together with the point through which it passes by a single press–drag–release sequence. When the mouse is pressed, the point is added. Dragging the mouse generates the line. It is always attached to the mouse pointer. When the mouse is released, the position of the line is frozen, and the construction is finished. More precisely:

- Pressing the left mouse button generates the point. The definition of this point depends on the position of the mouse at the moment the button is pressed:
- If the mouse pointer is over an existing point, then this point is taken.
- If the mouse pointer is over the intersection of two elements (line, circle, or conic), then this intersection is automatically constructed and taken as the point.
- If the mouse pointer is over just one element (line or circle), then a point is constructed that is constrained to this element. This point is taken as the point.
- Otherwise, a free point is added.
- Dragging the mouse generates the line. The slope can be adjusted freely. The line also snaps to existing points if they are selected by the current mouse position.
- Releasing the mouse button freezes the definition of the line. The construction is then finished. Depending on the final position of the mouse pointer, two things can happen:
- If the mouse pointer is over an existing point, then this point is used as a second point on the line. The line is then the "join" (connecting line) of the first and the second points.
- Otherwise, a "line with slope" is added.

#### Synopsis

Line through point mode creates a line through a point by a press–drag–release sequence.

#### See Also

- Add a Line
- Circle by Radius