Notations :
denotes the floor function .
denotes the fractional part function .
denotes the ceiling function .
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This problem is similar to this
Using a similar approach, we conclude that the given integral reduces to:
( r = 0 ∑ ∞ 2 r + 1 ( − 1 ) r ⋅ ( r + 1 ) ) ⋅ 2 0 1 6 ⋅ 2 1
⇒ 5 0 4 ⋅ ( r = 0 ∑ ∞ ( 2 − 1 ) r ⋅ ( r + 1 ) )
Let S = r = 0 ∑ ( 2 − 1 ) r ⋅ ( r + 1 )
⇒ S = 1 + 2 ( − 1 ) ( 2 ) + 2 2 ( 1 ) ( 3 ) + …
⇒ − 2 S = − 2 + 2 + 2 ( − 1 ) ( 3 ) + 2 2 ( 1 ) ( 4 ) + …
S − ( − 2 S ) = ( 1 − 0 ) + ( 2 ( − 1 ) ( 2 ) − 2 ( − 1 ) ( 3 ) ) + ( 2 2 ( 1 ) ( 3 ) − 2 2 ( 1 ) ( 4 ) ) + …
⇒ 3 S = 1 + 2 1 + 4 − 1 + …
⇒ 3 S = 1 + 1 − 2 − 1 2 1
⇒ S = 9 4
Hence, the given integral now reduces to:
5 0 4 ⋅ 9 4 = 2 2 4