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Help! I need the explanation if the answer is 72!!!

Help! I need the explanation if the answer is 72!!!-example-1
User Tonejac
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1 Answer

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∠72

Explanation:

  • It is isosceles Triangle.

Therefore Two sides will be equal

b = c ------

  • Given in the question - Angle b is twice the angle a.

=> ∠b = 2∠a

=> ∠a = ∠b/2 -------(1)

  • sum of two sides on isosceles Triangle is 180°

=> ∠a + ∠b + ∠c = 180

Put value of ∠a from equation (1)

=> ∠b/2 + ∠b + ∠b =180

[ look equation marked - ☆ ]

  • with LCM

=> 5∠b/2 = 180

=> 5∠b = 180 × 2

=> 5∠b = 360

=> ∠b = 360 / 5

=> 72

_______________

Some properties of Triangle-

  • two sides are equal.
  • two internal angles are equal.
  • two angles are opposite to equal side are equal.
  • sum of two angles 180°

_______________

User Verax
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