Question

如图在△ABC中,AB=AC,点D、E分别在AC、AB上,且BC=BD=DE=EA，求角A

如图

Answer 1

设∠C=∠ABC=x，∠DEB=∠DBE=y ，∠A=∠EDA=y/2
∠ADE+∠EDB +∠BDC=y/2 + 180-2y + x=180
x=3y/2

∠C+∠ABC+∠A=3y+ y/2 =180
y=360/7
那么∠A=180°/7