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← JEE Main 2014 · 6 Apr · Shift 1
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JEE Main 2014 · 6 Apr · Shift 1, Mathematics question 76

The area of the region described by A={(x,y):x2+y2≤1 and y2≤1−x}A=\{(x,y):x^2+y^2\le1\text{ and }y^2\le1-x\} is :

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Answer and worked solution

Official answer: C

The parabola y2=1−xy^2=1-x meets the circle where x2=xx^2=x, i.e. at x=0x=0 and x=1x=1.

  • For 0≤x≤10\le x\le1, 1−x≤1−x21-x\le1-x^2, so the parabola is the binding curve.
  • For x<0x<0, the circle is.

Area=π2⏟left half-disc+∫0121−x dx=π2+43.\text{Area}=\underbrace{\frac\pi2}_{\text{left half-disc}}+\int_0^12\sqrt{1-x}\,dx=\frac\pi2+\frac43.