Math help?
2017-03-19 8:49 pm
The diagram shows a regular Pentagon PQRST in a circle, centre O. The radius is 10 cm. Find angle QOR.
回答 (3)
2017-03-19 9:02 pm
✔ 最佳答案
The lines OP, OQ, OR, OS and OT divide the regular pentagon PQRST into 5 congruent triangles, i.e.ΔPOQ ≅ ΔQPR ≅ ΔROS ≅ ΔSOT ≅ ΔTOP
ie. ∠POQ = ∠QOR = ∠ROS = ∠ΔSOT = ∠ΔTOP
But ∠POQ + ∠QOR + ∠ROS + ∠ΔSOT + ∠ΔTOP = 360° (∠s at a pt.)
Hence, 5 ∠QOR = 360°
∠QOR = 72°
2017-03-19 9:08 pm
360/5 = 72 degrees
2017-03-19 8:56 pm
Since PQRST is regular, all the central angles
are equal, so each angle is 1/5 x 360 = 72º
(The radius is irrelevant)
are equal, so each angle is 1/5 x 360 = 72º
(The radius is irrelevant)
收錄日期: 2021-04-18 16:05:51
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