答：直角三角形ABC中：a+b+c=1,a>0,b>0,c>0a^2+b^2=c^2所以：a^2+b^2=c^2=[1-(a+b)]^2=1-2(a+b)+a^2+2ab+b^2整理得：2ab=2(a+b)-1>=2*2√(ab)-12[√(ab)]^2-4√(ab)+1>=02[√(ab)-1]^2>=1√(ab)-1>=√2/2或者√(ab)-...