Question
Question: \(\int_{0}^{\infty}{}\) [2 e<sup>-x</sup>]dx, where [.] denotes the greatest integer function, is eq...
∫0∞ [2 e-x]dx, where [.] denotes the greatest integer function, is equal to
A
0
B
ln 2
C
e2
D
2e–1
Answer
ln 2
Explanation
Solution
Since 0 < 2 e–x ≤ 2 ∀ x ∈ [0, ∞),
[2 e–x] = 0, for x > ln2.
Hence the given integral =∫0ln2dx+ 0 = ln 2