3-Point Rectangle
When you have digitised the position of the three points, the Rectangle Properties form is displayed:
First Point
If necessary, adjust the coordinates of the first point of the rectangle to alter its position.
First side
You can adjust the orientation and area of the rectangle by altering the angle and the length of its first side.
Second side
You can further adjust the area of the rectangle by altering the length of its second side.
Preview
Click the Preview button to see a preview of the rectangle. If you are happy with the result, click OK. Otherwise adjust the parameters you have entered and preview again.
When the Rectangle has been created, you can hover on it to display the properties of the new shape: