cosa=-√(1-m^2),tana=-m/√(1-m^2),tanb=-tan(π-b)=-n,tan2b=2tanb/[1-(tanb)^2]=-2n/(1-n^2),tan(a-2b)=(tana-tan2b)/(1+tanatan2b]=[-m/√(1-m^2)]/{1+[-m/√(1-m^2)][-2n/(1-n^2)]}=-2mn/[(1-n^2)√(1-m^2)+2mn...