延长线段ab到c点,使bc=⅓ab,反向延长ac到d点,使ad=½ac,则cd=多少ab

延长线段ab到c点,使bc=⅓ab,反向延长ac到d点,使ad=½ac,则cd=多少ab
延长线段ab到c点,使bc=⅓ab,反向延长ac到d点,使ad=½ac,则cd=多少ab

延长线段ab到c点,使bc=⅓ab,反向延长ac到d点,使ad=½ac,则cd=多少ab
∵BC＝AB/3
∴AC＝AB+BC＝AB+AB/3＝4AB/3
∵AD＝AC/2
∴AD＝（4AB/3）/2＝2AB/3
∴CD＝AD+AC＝4AB/3+2AB/3＝2AB

硬解设AC=b，BC=a，FC=x cos60=(1+b^2-x^2)/2b cos60=(4+b^2-a^2)/4b x^2=ab 解得b=1或b=0.5 (你的题目很难看)