tgA=BC/AC
0.8=12/AC
AC=12/0.8=15
AB=AC^2+BC^2=15^2+12^2=(15+12)(15+12)=27*27=3*9*3*9
AB=3^2*9^2=3*9=27
tgA=BC/AC
0.8=12/AC
AC=12/0.8=15
AB=AC^2+BC^2=15^2+12^2=(15+12)(15+12)=27*27=3*9*3*9
AB=3^2*9^2=3*9=27