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Length of proof is 13.  Level of proof is 7.

---------------- PROOF ----------------

7 [] -T(x,y,x)|x=y.
18 [] E(xa,xa,xb,xb).
20 [] xq=xa| -T(xq,xa,xd)| -E(xa,xd,xb,xc)|xd=ext(xq,xa,xb,xc).
24 [] T(xa,xb,xb).
107 [] M(xa,xm,xa)|xm!=xa.
136 [] -R(xa,xb,xa)|xa=xb.
139 [] -perpAt(xa,xb,xc,xp,xq)|perpAt(xp,xq,xc,xa,xb).
188 [] -M(xa,xm,xb)|T(xa,xm,xb).
202 [] -perpAt(y,z,x,y1,z1)|y!=z.
204 [] -perpAt(y,z,x,y1,z1)| -Col(y,z,u)| -Col(y1,z1,v)|R(u,x,v).
208 [] -perp(xp,xq,xp1,xq1)|perpAt(xp,xq,il(xp,xq,xp1,xq1),xp1,xq1).
211 [] perp(a,b,p,q).
212 [] Col(a,b,c).
213 [] Col(p,q,c).
214 [] -perpAt(a,b,c,p,q).
223 [binary,211.1,208.1] perpAt(a,b,il(a,b,p,q),p,q).
226 [binary,212.1,204.3] -perpAt(x,y,z,a,b)| -Col(x,y,u)|R(u,z,c).
292 [binary,214.1,139.2] -perpAt(p,q,c,a,b).
321 [binary,223.1,202.1] a!=b.
328 [binary,223.1,139.1] perpAt(p,q,il(a,b,p,q),a,b).
458 [binary,321.1,7.2] -T(a,b,a).
800 [binary,226.3,136.1] -perpAt(x,y,z,a,b)| -Col(x,y,c)|c=z.
1120 [binary,458.1,188.2] -M(a,b,a).
1497 [binary,1120.1,107.1] b!=a.
1571 [ur,20,1497,24,18] a=ext(b,a,x,x).
113174 [para_from,1571.1.1,328.1.3.1] perpAt(p,q,il(ext(b,a,x,x),b,p,q),a,b).
129496 [para_from,800.3.1,292.1.3] -perpAt(p,q,x,a,b)| -perpAt(y,z,x,a,b)| -Col(y,z,c).
129513 [factor,129496.1.2,unit_del,213] -perpAt(p,q,x,a,b).
129514 [binary,129513.1,113174.1] $F.