Question

中三数学几何证明题~有图1.ΔABC is a right-angled triangle with∠BAC=90度.A

Answer 1

(1).作DE⊥BC于E.∵BD=DC,∴DE是BC的中垂线.

设AD=x.∵AC^2=FC*BC,∴BC=(1+x)^2.

∵AC/BC=(BC/2)/CD,∴(1+x)/(1+x)^2=(1+x)^2/2,

(1+x)^3=2,AC=1+x=立方根2.

(2).延长BA到D,使AD=AC.HB=CA+AH=DA+AH=DH,

∠B=∠D=∠DCA,∠B+∠D+∠DCA+∠ACB=180,∠B=20度.