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The vertex of an equilateral triangle is (2, 3) and the equation of the opposite side is x + y = 2. Then the other two sides are y – 3 = (2±3)(x-2). - Mathematics

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Question

The vertex of an equilateral triangle is (2, 3) and the equation of the opposite side is x + y = 2. Then the other two sides are y – 3 = `(2 +- sqrt(3)) (x - 2)`.

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  • True

  • False

MCQ
True or False

Solution

This statement is True.

Explanation:

Let ABC be an equilateral triangle with vertex (2, 3) and the opposite side is x + y = 2 with slope –1.

Suppose slope of line AB is m.

Since each angle of equilateral triangle is 60°.

∴ Angle between AB and BC

tan 60° = `|(-1 - m)/(1 + (-1)m)|`

⇒ `sqrt(3) = |(1 + m)/(1 - m)|`

⇒ `sqrt(3) = +- ((1 + m)/(1 - m))`

Taking (+) sign,

`sqrt(3) = (1 + m)/(1 - m)`

⇒ `sqrt(3) - sqrt(3)m = 1 + m`

⇒ `sqrt(3)m + m = sqrt(3) - 1`

⇒ `m(sqrt(3) + 1) = sqrt(3) - 1`

⇒ `m = (sqrt(3) - 1)/(sqrt(3) + 1)

⇒ `m = (sqrt(3) - 1)/(sqrt(3) + 1) xx (sqrt(3) - 1)/(sqrt(3) - 1)`

⇒ `m = (3 + 1 - 2sqrt(3))/(3 - 1)`

= `2 - sqrt(3)`

Taking (–) sign,

`m = 2 + sqrt(3)`

So, the equations of other two lines are y – 3 = `(2 +- sqrt(3))(x - 2)`

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Chapter 10: Straight Lines - Exercise [Page 183]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 10 Straight Lines
Exercise | Q 52 | Page 183

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