:: deftheorem Def12 defines tricord2 EUCLID_3:def 12 :
for n being Element of NAT
for p1, p2, p3, p being Point of (TOP-REAL n) st p2 - p1,p3 - p1 are_lindependent2 & p in plane (p1,p2,p3) holds
for b₆ being Real holds
( b₆ = tricord2 (p1,p2,p3,p) iff ex a1, a3 being Real st
( (a1 + b₆) + a3 = 1 & p = ((a1 * p1) + (b₆ * p2)) + (a3 * p3) ) );