Prove that theorem 28 and theorem 29 hold for F_(3). (Farey series)
Theorem 28: If (h)/(k ) and (h')/(k') are two succesive terms of F_(n ), then kh'-hk'=1.
Theorem 29: If (h)/(k ), (h")/(k"), and (h')/(k') are three successive terms of F_(n), then (h")/(k")=(h+h')/(k+k').