Make Points A, B, C Collinear
Create two line segments on the plane such that[br][math]\frac{ }{AB}\frac{ }{\parallel}\frac{ }{CD}[/math]
Create two lines on the plane such that DB [math]\perp[/math] CA
Arrange point C and ray BD so that they are coplanar.
Make Points A, B, C Collinear, in that order. Now create ray CA and ray CB.
Create ray AB, add a point C on the ray so B is between A and C.
Create a plane by clicking on 3 points.
When can't you create a plane?
When the 3 points are in the same line. (Collinear)