Synthesis of 4 bar for 3 coupler's points

The approach has different stages that are explained below the image

Approach in several stages: 1.- From the 3 points and the inclination of the cranks, generate the coupler 2.- Solve the problem of synthesis of three positions of the coupler (first solution) 3.- To build the related mechanisms of the first solution (it is advisable to unclick the first two steps) 4.- Obtain the final solution of the synthesis problem (in red)