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Continuity And Differentiability

Question
CBSEENMA12036016

The area (in sq. units) of the regionopen curly brackets left parenthesis straight x comma straight y right parenthesis colon straight y squared space greater or equal than space 2 straight x space and space straight x squared space plus straight y squared space less or equal than 4 straight x comma space straight x space greater or equal than 0 comma space straight y greater or equal than 0 close curly brackets is

  • straight pi minus 4 over 3
  • straight pi minus 8 over 3
  • straight pi minus fraction numerator 4 square root of 2 over denominator 3 end fraction
  • straight pi over 2 minus fraction numerator begin display style 2 end style square root of 2 over denominator 3 end fraction

Solution

B.

straight pi minus 8 over 3
Given equations of curves are 
y2 = 2x ...(i)
which is a parabola with vertex (0,0) and parallel to X-axis and 
x2 +y2 = 4x  ... (ii)
which is a circle with centre (2,0) and radius = 2
on Substituting y2 = 2x in Eq (ii) we get
x2 + 2x = 4x
⇒ x2 +2x = 4x
⇒ x2 = 2x
⇒ x = 0 or x = 2
y =0 or y =±2 (using equ (i)]
Now, the required area is the area of shaded region, i.e,

Required space area space equals space fraction numerator Area space of space straight a space circle over denominator 4 end fraction space minus space integral subscript 0 superscript 2 square root of 2 straight x end root space dx
equals fraction numerator straight pi left parenthesis 2 right parenthesis squared over denominator 4 end fraction minus square root of 2 integral subscript 0 superscript 2 straight x to the power of 1 divided by 2 end exponent space dx
equals space straight pi space minus space square root of 2 open square brackets fraction numerator straight x to the power of 3 divided by 2 end exponent over denominator 3 divided by 2 end fraction close square brackets subscript 0 superscript 2
equals space straight pi space minus fraction numerator 2 square root of 2 over denominator 3 end fraction left square bracket 2 square root of 2 minus 0 right square bracket
equals open parentheses straight pi minus 8 over 3 close parentheses space sq space units

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