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JEE Main 20265 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
5 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Functions

JEE Main 2026 · 5 April · Evening Shift · Mathematics · Functions

Let f: R arrow R be a function such that f(x) + 3f((π)/(2) - x) = x...

Let f:R→Rf: \mathbf{R} \rightarrow \mathbf{R} be a function such that f(x)+3f(π2−x)=sin⁡xf(x) + 3f\left(\dfrac{\pi}{2} - x\right) = \sin x, x∈Rx \in \mathbf{R}. Let the maximum value of ff on R\mathbf{R} be α\alpha. If the area of the region bounded by the curves g(x)=x2g(x) = x^2 and h(x)=βx3h(x) = \beta x^3, β>0\beta > 0, is α2\alpha^2, then 30β330\beta^3 is equal to _______.

Correct answer

0

Step-by-step solution

Given f(x)+3f(π2−x)=sin⁡xf(x) + 3f\left(\dfrac{\pi}{2} - x\right) = \sin x

Replacing xx with π2−x\dfrac{\pi}{2} - x, we get:

f(π2−x)+3f(x)=sin⁡(π2−x)=cos⁡xf\left(\dfrac{\pi}{2} - x\right) + 3f(x) = \sin\left(\dfrac{\pi}{2} - x\right) = \cos x

Multiplying this equation by 33 and subtracting the first equation gives:

9f(x)−f(x)=3cos⁡x−sin⁡x9f(x) - f(x) = 3\cos x - \sin x

8f(x)=3cos⁡x−sin⁡x8f(x) = 3\cos x - \sin x

f(x)=3cos⁡x−sin⁡x8f(x) = \dfrac{3\cos x - \sin x}{8}

The maximum value of f(x)f(x) is α=32+(−1)28=108\alpha = \dfrac{\sqrt{3^2 + (-1)^2}}{8} = \dfrac{\sqrt{10}}{8}.

Thus, α2=1064=532\alpha^2 = \dfrac{10}{64} = \dfrac{5}{32}.

The points of intersection of the curves g(x)=x2g(x) = x^2 and h(x)=βx3h(x) = \beta x^3 are given by:

x2=βx3⇒x2(1−βx)=0⇒x=0,x=1βx^2 = \beta x^3 \Rightarrow x^2(1 - \beta x) = 0 \Rightarrow x = 0, x = \dfrac{1}{\beta}

The area of the region bounded by the curves is:

∫01/β(x2−βx3)dx=[x33−βx44]01/β\int_{0}^{1/\beta} (x^2 - \beta x^3) dx = \left[ \dfrac{x^3}{3} - \dfrac{\beta x^4}{4} \right]_{0}^{1/\beta}

=13β3−14β3=112β3= \dfrac{1}{3\beta^3} - \dfrac{1}{4\beta^3} = \dfrac{1}{12\beta^3}

Given that the area is α2\alpha^2, we have:

112β3=532\dfrac{1}{12\beta^3} = \dfrac{5}{32}

β3=3260=815\beta^3 = \dfrac{32}{60} = \dfrac{8}{15}

Therefore, 30β3=30×815=1630\beta^3 = 30 \times \dfrac{8}{15} = 16.

Answer: 1616
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