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JEE Main 20137 April
Exam
JEE Main
Year
2013
Date
7 April
Subject
Mathematics
Chapter
Straight Lines

JEE Main 2013 · 7 April · Mathematics · Straight Lines

The x - coordinate of the incentre of the triangle that has the...

The x−x -coordinate of the incentre of the triangle that has the coordinates of midpoints of its sides as (0,1),(1,1)and(1,0)is\left(0, 1\right), \left(1, 1\right) and \left(1, 0\right) isThe x - coordinate of the incentre of the triangle that has the coordinates of midpoints of its sides as (0, 1), (1, 1)

Options

  1. A1+21 + \sqrt{2}
  2. B1−21 - \sqrt{2}
  3. C2+22 + \sqrt{2}
  4. D2−22 - \sqrt{2}

Correct answer

D. 2−22 - \sqrt{2}

Step-by-step solution

The x - coordinate of the incentre of the triangle that has the coordinates of midpoints of its sides as (0, 1), (1, 1)

Let (x1,y1),(x2,y2)\left({x}_{1}, {y}_{1}\right), \left({x}_{2}, {y}_{2}\right) and \left({x}_{3}, {y}_{3}\right)betheverticesofatriangle,</p><p>So,<br/>be the vertices of a triangle,</p><p>So,<br />{x}_{1} + {x}_{2} = 0, {x}_{2} + {x}_{3} = 2, {x}_{3} + {x}_{1} = 2[midpointformula[mid point formula\dfrac{{x}_{1} + {x}_{2}}{2}]<br/><br/>Similarly,</p><p>]<br /><br />Similarly,</p><p>{y}_{1} + {y}_{2} = 2, {y}_{2} + {y}_{3} = 2, {y}_{3} + {y}_{1} = 0<br/><br/>So,theverticesare(0,0),(0,2),(2,0)<br /><br />So, the vertices are \left(0 ,0\right), \left(0 ,2\right), \left(2, 0\right).

We know that xx-coordinate of incentre x¯=ax1+bx2+cx3a+b+c\overset{¯}{x} = \dfrac{a{x}_{1} + b{x}_{2} + c{x}_{3}}{a + b + c}

a=2,b=2,c=22,x1=0,x2=2,x3=0a = 2, b = 2, c = 2\sqrt{2}, {x}_{1} = 0, {x}_{2} = 2, {x}_{3} = 0

∴x¯=0+4+02+2+22∴ \overset{¯}{x} = \dfrac{0 + 4 + 0}{2 + 2 + 2\sqrt{2}}

⇒ \overset{¯}{x} = \left(2 - \sqrt{2}\right)

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