tanA+tanB=-m, tanA •tanA=m+1
tanA+tanB -m
tan(A+B)=———————— = ———— = 1
1-tanA •tanA 1-m-1
∴tanC=-tan(180-C)=-tan(A+B)=-1
∴C=135°
tanA+tanB=-m, tanA •tanA=m+1
tanA+tanB -m
tan(A+B)=———————— = ———— = 1
1-tanA •tanA 1-m-1
∴tanC=-tan(180-C)=-tan(A+B)=-1
∴C=135°