theorem Th20: :: MATRTOP2:20

for n, k being Nat
for f being b₁ -element real-valued FinSequence
for B being OrdBasis of n -VectSp_over F_Real st B = MX2FinS (1. (F_Real,n)) holds
( f in Lin (rng (B | k)) iff f = (f | k) ^ ((n -' k) |-> 0) )