In Diagram I below, ABCDEABCDE is a regular pentagon, centre OO. OA=OB=4 cmOA = OB = 4\text{ cm}. (a) State the value of angle AOBAOB. Answer Angle AOBAOB = ___ ∘^\circ

Properties shapes

Worked solution

(a)

1. 计算正五边形的中心角 $\angle AOB$

正五边形 ABCDEABCDE 的中心 OO 周围的周角 360∘360^\circ 被分成 55 个相等的中心角。
∠AOB=360∘5=72∘\angle AOB = \frac{360^\circ}{5} = 72^\circ

Answer

72∘72^\circ

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