1. Do you know how to change lengths of links in to get one (strictly) straight line of motion for point 4 or other curve? See please first animation and files in attach - Mathcad 15. I have a plan use the MinErr function but not too simple!
2. Why I have an error by changing L14? See the animation two. When I use not the solve operator but the Find (numeric) function - no problem (see the animation 3)