Attaching a Straight Object to an Existing Object

You can attach either the first or second determining point of a straight object to an existing object. To do so, you can click

· an existing point

· a path object such as a segment, a line, a circle, or an arc

· an intersection of two path objects.

When the Straightedge tool is in the right place to click on an existing object, that object is highlighted, appearing thicker and in a special color.

Be careful when you want to attach a defining point to an existing object. It’s not enough to position the tool so that the ray or line appears to go through the desired location. You must actually position the tool itself over the object to which you want to attach before clicking or releasing the mouse to locate the defining point.

For example, a student wants to draw a diagonal line passing through the intersection of the horizontal and vertical lines. In the following illustration, even though the line in the left box appears to pass through the intersection, the cursor is positioned to click in empty space, so the second defining point of the line won’t be attached. But the cursor in the right box is over the intersection, so the intersecting lines are highlighted, and when clicked on, the point will be defined at the intersection.

Line not attached to intersection

Line attached to intersection

In another example, a student wants to attach a ray’s through point to the circle so the through point can be animated around the circle. The next illustration shows how to accomplish this. Positioning the cursor to click where shown in the left box won’t work because the through point will not be attached to the circle. Clicking where shown in the right box, with the cursor over the circle and the circle highlighted, defines the point on the circle.

Ray not attached to circle

Ray attached to circle