显然AE=BE=AD/cosA=(1/2)AB/cos40°
AB+AE+BE=AB+2AE=[(1+2cos40°)/cos40°]*AB=50
AB=50cos40°/(1+2cos40°)
AC=AB=50cos40°/(1+2cos40°)
BE+EC+BC=AE+EC+BC=AC+BC=30
BC=30-AC=30-50cos40°/(1+2cos40°)
显然AE=BE=AD/cosA=(1/2)AB/cos40°
AB+AE+BE=AB+2AE=[(1+2cos40°)/cos40°]*AB=50
AB=50cos40°/(1+2cos40°)
AC=AB=50cos40°/(1+2cos40°)
BE+EC+BC=AE+EC+BC=AC+BC=30
BC=30-AC=30-50cos40°/(1+2cos40°)