> addvertex(T4,theory);

T4

> addedge([RA,T4],theory);

e4

> addedge([PS,T4],theory);

e5

> addedge([T1,T4],theory);

e6

> mylin([[I1,I2,RA,PS],[T1,T2,T3],[T4]],theory,[0,0],blue,3);