# 圓心角與扇形 - PowerPoint PPT Presentation

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1.從旋轉角到平角、周角。

2.何謂圓心角？

3.何謂扇形？

1.圓心為頂點

2.兩條半徑為兩邊

→以兩條半徑所夾的角就是圓心角

×

1.圓心為頂點

2.兩條半徑為兩邊

×

1.圓心為頂點

2.兩條半徑為兩邊

1.圓心為頂點

2.兩條半徑為兩邊

×

1.圓心為頂點

2.兩條半徑為兩邊

×

1.兩條半徑

2.一段圓弧

3600 B

1.圓心角為30度

2.圓心角為45度

3.圓心角為60度

4.圓心角為120度

→十二分之一的圓

→八分之一的圓

→六分之一的圓

→三分之一的圓

### 二、下列扇形的圓心角各是幾度？

A

圓心角＝ 3600 × ── 的圓

B

1.三分之一的圓

2.六分之五的圓

3.八分之一的圓

→圓心角是120度

→圓心角是300度

→圓心角是45度