(1)
∠ADE=∠C,∠A=∠A
所以△ABC∽△AED
(2)
AD/AC=AE/AB
AC=AE+CE=AE+y
即x/(AE+y)=AE/5
割线定理:AE*AC=x*5 (余弦定理求出AC=7)
则AE=5x/7,代入
化简得y=7-5x/7 0
(1)
∠ADE=∠C,∠A=∠A
所以△ABC∽△AED
(2)
AD/AC=AE/AB
AC=AE+CE=AE+y
即x/(AE+y)=AE/5
割线定理:AE*AC=x*5 (余弦定理求出AC=7)
则AE=5x/7,代入
化简得y=7-5x/7 0