∫ 0 ∞ e − x 8 cos ( x 8 ) x 3 ln ( x ) d x If the integral above can be expressed as B − π A 1 [ A + C ( γ C + A D ln ( A ) ) + E π C A − C ]
with positive integers A , B , C , D , E and all fractions are irreducible and A being square free, then evaluate A + B + C + D + E .
Notation: γ ≈ 0 . 5 7 7 2 denotes the Euler-Mascheroni constant .
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The answer is: 1 2 8 − π 2 1 [ 2 + 1 ( γ + 2 5 ln ( 2 ) ) + 4 π 2 − 1 ] Will post the solution later
your problems are good! is this original?
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yes, I created it at around 4 AM , I wasn't feeling sleepy!
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The substitution u = x 8 makes the integral I = 6 4 1 ∫ 0 ∞ e − u cos u u − 2 1 ln u d u = 6 4 1 A ′ ( 2 1 ) where A is the function A ( a ) = ∫ 0 ∞ e − u cos u u a − 1 d u = 2 − 2 1 a cos 4 π a Γ ( a ) a > 0 . Differentiating and simplifying, we obtain A ′ ( 2 1 ) I = = − 2 4 5 π cos 8 π ln 2 + 2 4 1 π cos 8 π ψ ( 2 1 ) − 2 4 1 7 π π sin 8 π − 1 2 8 π [ 2 + 1 ( γ + 2 5 ln 2 ) + 4 1 π 2 − 1 ] making the answer 2 + 1 2 8 + 1 + 5 + 4 = 1 4 0 .