Question
Question: \(\int _ { 0 } ^ { \infty }\)[2 e<sup>-x</sup>] dx, where [.] denotes the greatest integer function,...
∫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