Let f: R → R be a function such that f(x) + 3f ( π 2 - x ) = sin x, x ∈ R. Let the maximum value of f on R be α. If the area of the region bounded by…
JEE Main 2026 — Mathematics Algebra
2026integermedium
Let f:R→R be a function such that f(x)+3f(2π−x)=sinx, x∈R. Let the maximum value of f on R be α. If the area of the region bounded by the curves g(x)=x2 and h(x)=βx3, β>0, is α2, then 30β3 is equal to _______.
Official previous-year question
Held on 5 Apr 2026 · Verified 6 Jul 2026.
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Solution
Given f(x)+3f(2π−x)=sinx
Replacing x with 2π−x, we get:
f(2π−x)+3f(x)=sin(2π−x)=cosx
Multiplying this equation by 3 and subtracting the first equation gives:
9f(x)−f(x)=3cosx−sinx
8f(x)=3cosx−sinx
f(x)=83cosx−sinx
The maximum value of f(x) is α=832+(−1)2=810.
Thus, α2=6410=325.
The points of intersection of the curves g(x)=x2 and h(x)=βx3 are given by:
x2=βx3⇒x2(1−βx)=0⇒x=0,x=β1
The area of the region bounded by the curves is:
∫01/β(x2−βx3)dx=[3x3−4βx4]01/β
=3β31−4β31=12β31
Given that the area is α2, we have:
12β31=325
β3=6032=158
Therefore, 30β3=30×158=16.
Answer: 16
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