Question

如图,三角形ABC,角A=60度,AC=2,CD垂直AB,任意做角EDF=60度,E,F在边AB,AC上设AB=x,BF

Answer 1

如图

∵∠A=∠FDE=60°

又∵CD⊥AB,EF⊥AD

∴∠AFE=∠ACD=∠FDC=30°

∠FDB=∠CFD=120°

∴△AFD是等边△ 且 FC=FD=FA=1

∵△CFD≌△BDF

∴CF=BD,

∴△ACD≌△ABF

∴Y²=X²-1