Matching Given Objects

Tools can use as their givens various kinds of objects: points, straight objects, circles, measurements, functions, and so forth. When you use a tool, a message appears on Sketchpad’s status line at the bottom of the window describing what kind of given object you need to match next.

The status line can help you figure out what to match next.

For example, if a tool uses a point, a segment, and a distance measurement as its three givens, the status line first says “1. Match Point…” to indicate what object you must match first. After you match the point, the status line says “2. Match Segment…” to indicate that you must next specify a segment. And finally, it says “3. Match Distance Measurement…” when it’s time for you to click on a distance measurement as the last given object.

You can always match a given by clicking on a sketch object of the correct kind. For some givens—points, straight objects, and circles—you can also match the given by constructing it.

If a given object for a tool is a point, you can specify it in either of two ways.

· Specify an existing point: Click on an existing point in the sketch. The point you click on is used as the given.

· Construct a new point: Click somewhere else in the sketch—in empty space, on a path, or at an intersection—to construct a new point. The point you construct is used as the given.

If a given object for a tool is a circle or straight object, you can specify it in either of two ways.

· Specify an existing object: Click on an existing object of the correct kind. The object you click on is used as the given.

· Construct a new object: Click twice (or press and drag) in the sketch to specify the two points which determine the given. If you’re constructing a circle given, the first point is the center and the second point is the radius point. If you’re constructing a straight object, the two points are the two determining points of the straight object.

If the given for a tool is any other kind of object, you must click on a matching object in the sketch. If no object of the correct kind exists in the sketch, you must create such an object before you can use the tool.