Prove that the lines y = √3x + 1, y = 4 and y = -√3x + 2 form an equilateral triangle.
Prove that the lines y = √3x + 1, y = 4 and y = -√3x + 2 form an equilateral triangle.

Given:

    \[y\text{ }=\text{ }\surd 3x\text{ }+\text{ }1\ldots \ldots \text{ }\left( 1 \right)\]

    \[y\text{ }=\text{ }4\text{ }\ldots \ldots .\text{ }\left( 2 \right)\]

and

    \[y\text{ }=\text{ }\text{ }\surd 3x\text{ }+\text{ }2\ldots \ldots .\text{ }\left( 3 \right)\]

assume in triangle ABC,

equations (1), (2) and (3) represent the sides AB, BC and CA, respectively.

By solving equations (1) and (2), we have

    \[x\text{ }=~\surd 3,\text{ }y\text{ }=\text{ }4\]

Thus,

AB and BC intersect at B(√3,4)

Now, solving equations (1) and (3), we have

    \[x\text{ }=\text{ }1/2\surd 3,\text{ }y\text{ }=\text{ }3/2\]

Thus, AB and CA intersect at A (1/2√3, 3/2)

Similarly, solving equations (2) and (3), we get

    \[x\text{ }=\text{ }-2/\surd 3,\text{ }y\text{ }=\text{ }4\]

Thus, BC and AC intersect at C (-2/√3,4)

Now, we have:

Hence proved,

RD Sharma Solutions for Class 11 Maths Chapter 23 – The Straight Lines - image 58

the given lines form an equilateral triangle.