B、D分别是AC,CE的中点,
AC=8cm,BC=8/2=4cm
CE=6cm,CD=6/2=3cm
BD=BC+CD=4+3=7cm
BD=BC+CD=a/2+b/2=(a+b)/2
BD=BC+CD=AC/2+CE/2=(AC+CE)/2=AE/2
B、D分别是AC,CE的中点,
AC=8cm,BC=8/2=4cm
CE=6cm,CD=6/2=3cm
BD=BC+CD=4+3=7cm
BD=BC+CD=a/2+b/2=(a+b)/2
BD=BC+CD=AC/2+CE/2=(AC+CE)/2=AE/2