Constrict all vertices of a triangle cannot cross the edges of the triangle
Hi, I have a question related to vertices of a triangle.
I knew there is a PointIn Command that constraints the movement of a point within a shape. I have draft an attached file showing that vertices A cannot cross the edges BC. However, when I practice the same trick again for vertices B or C, the triangle will transform to a line. When I adjust the position of B and C, the PointIn command in the properties of point B and C disappears.
Is that any method that can prevent vertices crossing all three edges in triangle? Thanks for your help.