解答:
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/29381f30e924b89997de97896d061d950b7bf6a5?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
解:当弦AB与CD在圆心O的异侧时,如图1所示,
过O作EF⊥AB,由AB∥CD,得到EF⊥CD,
则E为AB中点,F为CD中点,即AE=BE=
AB=3cm,CF=DF=
CD=4cm,
在Rt△AOE中,OA=5cm,AE=3cm,
根据勾股定理得:OE=4cm,
在Rt△COF中,OC=5cm,CF=4cm,
根据勾股定理得:OF=3cm,
此时两平行弦AB、CD间的距离EF=OE+OF=4+3=7(cm);
当弦AB与CD在圆心O的同侧时,如图2所示,同理可得EF=OE-OF=4-3=1(cm),
综上,两平行弦AB、CD间的距离等于7cm或1cm.
故选D.