Prove that triangle ABC is isosceles, angle BCO = 140 degrees, angle DAN = 40 degrees.
| August 22, 2021 | education
Angle DAн = BAC as vertical angles at the intersection of straight lines BH and DO.
The angle BCO is adjacent to the angle ACB, the sum of which is 180, then the angle ACB = (180 – 140) = 40.
In the triangle ABC, the angle BAC = ACB, hence the triangle ABC is isosceles with the base AC, which was required to be proved.
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