Drawing elliptical arcs by rectangle

You can construct an elliptical arc by drawing its "parent" ellipse by rectangle first: you draw an ellipse that is inscribed in an auxiliary rectangle by positioning the four angle points of the circumscribing rectangle. The ellipse is defined by its primary and secondary radii, and the angle between the primary radius and the x-axis.

When the "parent" ellipse is ready, the elliptical arc is defined by the Start and End points of the elliptical arc curve (they could lie anywhere on the circumference of the "parent" ellipse that the arc belongs to). The Start and End points are defined by the angle values formed by the two respective radii (connecting the start and end points with the center) against the Ox coordinate axis.

Control points

An ellipse constructed by rectangle has six control points: the four vertices of the rectangle circumscribing the "parent" ellipse, and the starting and end points of the elliptical arc itself. While you are drawing an ellipse by rectangle, the following mouse pointers appear:

About to draw the first vertex of the circumscribing rectangle.

About to draw the second vertex of the circumscribing rectangle.

About to draw the third vertex of the circumscribing rectangle.

About to mark the starting point of the elliptical arc.

About to mark the end point of the elliptical arc.

To draw an elliptical arc by rectangle

1. Do any of the following:

• On the Objects toolbar, click  Elliptical Arc by Rectangle .
• On the Objects menu, point to Elliptical Arcs, and then click Elliptical Arc by Rectangle.

2. Define the "parent" ellipse:
   1. Snap the vertex point of the circumscribing rectangle that you are about to place, to another object or point.
   2. Place the first vertex of the circumscribing rectangle.
   3. Repeat Steps i. and ii. until you have defined three arbitrary vertices that define the circumscribing rectangle of the "parent" ellipse.

3. Specify the starting and end points of the elliptical arc by doing one of the following:

• Rotate the mouse pointer clockwise along the ellipse circumference and click where you want the two points to be.
• Enter values for Start and End angles in the contextual edit bar, and click to set them.
• Snap these points to other objects or points.

To modify an elliptical arc by changing its attributes

1. Select the elliptical arc.
2. In the contextual edit bar, enter attribute values, and then press ENTER.

To modify an elliptical arc by modifying its circumscribing rectangle

1. Point to the elliptical arc to detect the vertices of the rectangle circumscribing the "parent" ellipse.
2. Click on a vertex, drag it to where you want it to be, and click to place the modified elliptical arc.

To reposition an elliptical arc by dragging

1. Select the elliptical arc.
2. Do any of the following:

• Drag the elliptical arc to where you want it to be.
• In the contextual edit bar, in Dx and Dy enter offset distances relative to the original location of the elliptical arc.

3. Click to place the elliptical arc in its new location.

NOTE: If the control points of the elliptical arc (these are the vertices of the circumscribing rectangle) coincide with the control points of other objects — for example, when the elliptical arc is inscribed into a design box — the elliptical arc is repositioned and the connected objects are modified depending on the direction and distance at which you drag the elliptical arc.