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JEE Main 201912 JanuaryMorning Shift
Exam
JEE Main
Year
2019
Date
12 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Circle

JEE Main 2019 · 12 January · Morning Shift · Mathematics · Circle

Let C _ 1 and C _ 2 be the centres of the circles x ^ 2 + y ^ 2 -...

Let C1{C}_{1} and C2{C}_{2} be the centres of the circles x2+y2−2x−2y−2=0{x}^{2} + {y}^{2} - 2x - 2y - 2 = 0 and x2+y2−6x−6y+14=0{x}^{2} + {y}^{2} - 6x - 6y + 14 = 0 respectively. If PP and QQ are the points of intersection of these circles, then the area (in sq. units) of the quadrilateral PC1QC2P{C}_{1}Q{C}_{2} is :Let C _ 1 and C _ 2 be the centres of the circles x ^ 2 + y ^ 2 - 2x - 2y - 2 = 0 and x ^ 2 + y ^ 2 - 6x - 6y + 14 = 0

Options

  1. A66
  2. B44
  3. C88
  4. D99

Correct answer

B. 44

Step-by-step solution

Equation of given circles are

(x−1)2+(y−1)2=4{\left(x - 1\right)}^{2} + {\left(y - 1\right)}^{2} = 4 and (x−3)2+(y−3)2=4{\left(x - 3\right)}^{2} + {\left(y - 3\right)}^{2} = 4.

Let C _ 1 and C _ 2 be the centres of the circles x ^ 2 + y ^ 2 - 2x - 2y - 2 = 0 and x ^ 2 + y ^ 2 - 6x - 6y + 14 = 0

Hence, C1(1,1){C}_{1}\left(1, 1\right) and r1=2{r}_{1} = 2; C2(3,3){C}_{2}\left(3, 3\right) and r2=2{r}_{2} = 2

⇒PC1=PC2=2⇒ P{C}_{1} = P{C}_{2} = 2

Now, by distance formula,

C1C2=(3−1)2+(3−1)2=22+22=8{C}_{1}{C}_{2} = \sqrt{{\left(3 - 1\right)}^{2} + {\left(3 - 1\right)}^{2}} = \sqrt{{2}^{2} + {2}^{2}} = \sqrt{8}

⇒PC12+PC22=C1C22⇒ P{C}_{1}^{2} + P{C}_{2}^{2} = {C}_{1}{C}_{2}^{2}

⇒∠C1PC2=π2⇒ ∠{C}_{1}P{C}_{2} = \dfrac{\pi}{2} (by converse of pythagoras theorem in △PC1C2△ P{C}_{1}{C}_{2})

Hence, area of quadrilateral PC1QC2=2×P{C}_{1}Q{C}_{2} = 2 \timesarea of △PC1C2=2×△ P{C}_{1}{C}_{2} = 2 \timesarea of △QC1C2△ Q{C}_{1}{C}_{2}

=2×12×2×2=4= 2 \times \dfrac{1}{2} \times 2 \times 2 = 4

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