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  1. Chapter 11 Class 9 Constructions
  2. Serial order wise


Construction 11.3 : To construct an angle of 60° at the initial point of a given ray. Steps of Construction : Draw a ray AB with initial point A 2. Taking A as centre and some radius, draw an arc, which intersects AB at Point D. 3. Taking D as Centre and with the same radius as before, draw an arc intersecting the previously drawn arc at point E. 4. Draw the ray AC Passing through E. Thus, ∠CAB = 60° Justification We need to prove ∠ CAB = 60° Join DE. Since Arc AD = Arc AE and using same radius, we drew arc DE Thus, their radius will be the same ∴ AE = AD = DE Therefore, ∆ EAD is an equilateral triangle ∴ ∠EAD = 60° ⇒ ∠CAB = 60°. Hence justified

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.