Q60 / 90 · JEE Main 2022 (25 Jun Shift 2) · Mathematics

If the angle made by the tangent at the point x0,y0 on the curve x=12t+sintcost,
y=121+sint2,0<t<π2, with the positive x-axis is π3, then y0 is equal to

  • A
    63+22
  • B
    37+43
  • Correct answer
    C
    27
  • D
    48

Solution

Given, 

Curve x=12t+sintcost

y=121+sint2

Now dydx=dydtdxdt

tanπ3=ddt121+sint2ddt12t+sintcost

3=12×21+sintcost121+cos2t

3=21+sint·cost2cos2t

3=1+sintcost=cost2+sint22cos2t2-sin2t2

3=tant2+π4

π3=t2+π4 ⇒t2=π12 ⇒ t=π6

Now putting t=π6 in y=121+sint2

as x0,y0 lie on curve

So y0=121+sinπ62

=12322=27

Hence, the correct answer is option: 'C'.

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