已知線段AB=10cm,點(diǎn)C是直線AB上一點(diǎn),BC=4cm,若M是AC的中點(diǎn),N是BC的中點(diǎn),則線段MN的長(zhǎng)度是( ?。?br/>A. 7cm
B. 3cm
C. 7cm或3cm
D. 5cm
(1)當(dāng)點(diǎn)C在線段AB上時(shí),則MN=
AC+
BC=
AB=5;
(2)當(dāng)點(diǎn)C在線段AB的延長(zhǎng)線上時(shí),則MN=
AC-
BC=7-2=5.
綜合上述情況,線段MN的長(zhǎng)度是5cm.
故選D.