Find the value of the above integral, to 2 decimal places if necessary.
Notation:
denotes the
ceiling function
.
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I = ∫ 0 ∞ ⌈ x ⌉ 2 x d x = ∫ 0 1 1 ⋅ 2 x d x + ∫ 1 2 2 ⋅ 2 x d x + ∫ 2 3 3 ⋅ 2 x d x + ⋯ = r = 1 ∑ ∞ ∫ r − 1 r r ⋅ 2 x d x = ln 2 1 r = 1 ∑ ∞ r ⋅ 2 r 1
ln ( 1 + x ) − ln ( 1 − x ) = x − 2 x 2 + 3 x 3 − ⋯ = x + 2 x 2 + 3 x 3 + ⋯
ln 2 = 2 1 + 2 ⋅ 2 2 1 + 3 ⋅ 2 3 1 + ⋯ = r = 1 ∑ ∞ r ⋅ 2 r 1
I = ln 2 1 × ln 2 = 1