NVAMediumJEE 2023Applications of Integrals (Area)

JEE Mathematics 2023 Question with Solution

If the area of the region S = {(x,yx,y): 2yy2x2y2y - y^2 \leq x \leq 2y, xyx \geq y} is equal to (11n)π4\frac{\left(1 - \frac{1}{n}\right)\pi}{4}, then the natural number nn is equal to:

Answer

Correct answer:5

Step-by-step solution

Standard Method

Given: The region is S={(x,y):2yy2x2y, xy}S = \{(x,y): 2y - y^2 \leq x \leq 2y,\ x \geq y\}.

Find: The natural number nn if the area is (11n)π4\frac{\left(1-\frac{1}{n}\right)\pi}{4}.

From the extracted solution, the inequalities are rewritten as

x2+y22y0,x22y0,xyx^2 + y^2 - 2y \geq 0,\quad x^2 - 2y \leq 0,\quad x \geq y

Required Area Calculation:

Required Area=12×2×222x22dxπ412\text{Required Area} = \frac{1}{2} \times 2 \times 2 - \int_{2}^{2} \frac{x^2}{2} \, dx - \frac{\pi}{4} - \frac{1}{2}

Simplifying:

=76π4= \frac{7}{6} - \frac{\pi}{4}

The extracted solution then concludes

n=5n = 5

Therefore, the natural number is 55.

the solution extraction note

The solution appears partially corrupted and includes malformed text such as strong>Given Function: and an integral with identical limits 22 to 22. Using the provided extracted conclusion, the final answer obtained on the solution's is n=5n = 5.

Common mistakes

  • Interpreting the region directly without converting each boundary carefully can lead to a wrong sketch. First identify the curves represented by x=2yy2x = 2y - y^2, x=2yx = 2y, and the line x=yx = y before finding the enclosed area.

  • Using the given area form incorrectly is a common error. Since the area is already stated as (11n)π4\frac{\left(1-\frac{1}{n}\right)\pi}{4}, compare the computed area with this exact expression before solving for nn.

  • Ignoring that the solution is malformed can cause invalid algebraic manipulation. When a derivation contains corrupted limits or symbols, rely only on the clearly recoverable mathematical statements and the verified final conclusion.

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