Basically what you need are:
1. Get the Infinity line of lines AC and BD.
2. Get the intersection point of lines AC and BD.(2nd point).
3. After saving the intersection point choose the infinity lines between A,B,C and D depending on your constraint then make an infinity out of it (3rd point).
4. Go back to your line to serve as a point 1
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solved How to make a triangle pattern drawing