DE=-a
AD=a+b
BC=(a+b)/2
EF=-BC=-(a+b)/2
FA=(a-b)/2
CD=-FA=-(a-b)/2
AC=AB+BC=a+(a+b)/2=1.5a+0.5b
CE=CD+DE=-a+(-(a-b)/2)=-1.5a+0.5b
OK?
DE=-a
AD=a+b
BC=(a+b)/2
EF=-BC=-(a+b)/2
FA=(a-b)/2
CD=-FA=-(a-b)/2
AC=AB+BC=a+(a+b)/2=1.5a+0.5b
CE=CD+DE=-a+(-(a-b)/2)=-1.5a+0.5b
OK?