let T be non empty pathwise_connected TopSpace; for y0, y1 being Point of T
for R, V being Path of y0,y1 st R,V are_homotopic holds
pi_1-iso R = pi_1-iso V
let y0, y1 be Point of T; for R, V being Path of y0,y1 st R,V are_homotopic holds
pi_1-iso R = pi_1-iso V
let R, V be Path of y0,y1; ( R,V are_homotopic implies pi_1-iso R = pi_1-iso V )
y0,y1 are_connected
by BORSUK_2:def 3;
hence
( R,V are_homotopic implies pi_1-iso R = pi_1-iso V )
by Th49; verum