圆的弦与直径相交成30度角，并且分直径为8cm和2cm两部分，则弦心距是______cm．
根据题意画出相应的图形，如图所示：
由题意得到AM=8cm，BM=2cm，
∴AB=AM+BM=10cm，
∴OB=5cm，即OM+MB=5cm，
∴OM=502=3cm，
过O作OE⊥CD，交CD于点E，
在Rt△OME中，OM=3cm，∠OME=30°，
∴OE=
OM=1.5cm．1 2
故答案为：1.5
| 用方框内所给词的适当形式填空。 | |
to all their questions. We will all have 2_____ at our homes. So we'll be 3_____ to let robots do most of the 4_____ While making a telephone call, we'll also be able to see the people on the 5_____ end at the same time. A lot of people will live and work under sea or in 6_____ because there will be big towns and 7_____ there. Robots will do most of the work,and people will just 8_____ two. or three days a week. They'll be able to 9_____ to the moon in a spaceship and 10_____ their holidays there. |