a=m^2+n^2 b=m^2-n^2 c=2mn b^+c^2=(m^2-n^2)^2+(2mn)^2 =m^4-2m^2*n^2+n^4+4m^2*n^2 =m^4+2m^2*n^2+n^4=(m^2+n^2)=a^2 即:b^2+c^2=a^2 所以三角形ABC为直角三角形
∵(m^2-n^2)^2+(2mn)^2=m^4-2m^2*n^2+n^4+4m^2*n^2=m^4+2m^2*n^2+n^4=(m^2+n^2)^2∴三角形为直角三角形