JAMIA 2023 — Mathematics PYQ
JAMIA | Mathematics | 2023The value of ∫0πx(sin4xcos4x)dx is
Choose the correct answer:
- A.
643π2
- B.
1283π2
- C.
2563π2
Explanation
Given:
I=∫0πx(sin4xcos4x)dx
Step 1: Property ∫0af(x)dx=∫0af(a−x)dx ka use karke:
I=∫0π(π−x)sin4(π−x)cos4(π−x)dx
I=∫0π(π−x)sin4xcos4xdx…(1)
I=∫0πxsin4xcos4xdx…(2)
Step 2: Dono equations ko add karne par:
2I=∫0π(x+π−x)sin4xcos4xdx
2I=π∫0πsin4xcos4xdx
I=2π∫0πsin4xcos4xdx
Step 3: Symmetry property ∫02af(x)dx=2∫0af(x)dx use karke:
I=2π⋅2∫0π/2sin4xcos4xdx
I=π∫0π/2sin4xcos4xdx
Step 4: Wallis' Formula apply karne par:
Formula: ∫0π/2sinmxcosnxdx=(m+n)!!(m−1)!!(n−1)!!⋅2π
Yahan m=4,n=4:
∫0π/2sin4xcos4xdx=8⋅6⋅4⋅2(3⋅1)(3⋅1)⋅2π
∫0π/2sin4xcos4xdx=3849⋅2π=1283⋅2π=2563π
Step 5: Final calculation:
I=π(2563π)
I=2563π2
Explanation
Given:
I=∫0πx(sin4xcos4x)dx
Step 1: Property ∫0af(x)dx=∫0af(a−x)dx ka use karke:
I=∫0π(π−x)sin4(π−x)cos4(π−x)dx
I=∫0π(π−x)sin4xcos4xdx…(1)
I=∫0πxsin4xcos4xdx…(2)
Step 2: Dono equations ko add karne par:
2I=∫0π(x+π−x)sin4xcos4xdx
2I=π∫0πsin4xcos4xdx
I=2π∫0πsin4xcos4xdx
Step 3: Symmetry property ∫02af(x)dx=2∫0af(x)dx use karke:
I=2π⋅2∫0π/2sin4xcos4xdx
I=π∫0π/2sin4xcos4xdx
Step 4: Wallis' Formula apply karne par:
Formula: ∫0π/2sinmxcosnxdx=(m+n)!!(m−1)!!(n−1)!!⋅2π
Yahan m=4,n=4:
∫0π/2sin4xcos4xdx=8⋅6⋅4⋅2(3⋅1)(3⋅1)⋅2π
∫0π/2sin4xcos4xdx=3849⋅2π=1283⋅2π=2563π
Step 5: Final calculation:
I=π(2563π)
I=2563π2

