ABCD和OEFG为两个全等的正方形．O是正方形ABCD的中心点，若ÐEOB=22.5°，AB=1公分．试求阴影部分的面积．
计算下面各题． ．
= × ==．
口算显身手．×2=×== 12﹣=×= 1×=×0= 3×=×=
口算题．×12=×= 60×=×=
．
= × =
=
．
×2=
×
=
=
=
×
= 1×
=
×0= 3×
=
×
=
×12=
×
=
=
×
=
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