theorem Th21: :: MATRTOP3:21

for r being Real
for i, j, n being Nat
for p being Point of (TOP-REAL n) st 1 <= i & i < j & j <= n holds
((Mx2Tran (Rotation (i,j,n,r))) . p) . i = ((p . i) * (cos r)) + ((p . j) * (- (sin r)))