JEE Advanced2016MathematicsDefinite IntegrationActual
The value of ∫ - π 2 π 2 x 2 cos ⁡ x 1 + e x d x is equal to
Options
- Aπ 2 4 - 2
- Bπ 2 4 + 2
- Cπ 2 - e π 2
- Dπ 2 + e π 2
Correct answer
A. π 2 4 - 2
Step-by-step solution
Let I = ∫ −   x 2 x 2 x 2 cos x 1 + e x d x Replacing x by - x I = ∫ − π 2 π 2 ( x 2 cos x 1 + e − x ) d x ⇒ 2 I = ∫ − π 2 π 2 ( 1 1 + e x + 1 1 + e − x ) x 2 cos x   d x ⇒ 2 I = ∫ − π 2 π 2 x 2 cos x   d x , (even function) I =   ∫ 0 π 2 x 2 cos ⁡ x   d x = x 2 sin ⁡ x 0 π 2 - 2 ∫ 0 π 2 x . sin ⁡ x   d x (Using integration by parts, taki