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In the given figure, if ABC is an equilateral triangle. Find ∠BDC and ∠BEC. - Mathematics

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Question

In the given figure, if ABC is an equilateral triangle. Find ∠BDC and ∠BEC.

Short Note

Solution

It is given that, ABC is an equilateral triangle

We have to find `angleBDC`   and  `angleBEC`

Since  ΔABC  is an equilateral triangle

So, `angleA = angleB = angleC = 60°`

And  ABEC  is cyclic quadrilateral

So    `angle A + angle E = 180°`  (Sum of opposite pair of angles of a cyclic quadrilateral is 180°.)

Then,

`angle E = 180° - 60°`

      = 120°

Similarly BECD is also cyclic quadrilateral

So,

`angle E + angle D = 180°`

               `angleD = 180° - 120°`

                            = 60°

Hence, `angle BDC `= 60° and  `angle BEC = 120°`.

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Chapter 15: Circles - Exercise 15.5 [Page 102]

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RD Sharma Mathematics [English] Class 9
Chapter 15 Circles
Exercise 15.5 | Q 13 | Page 102
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