If ∫ 0 2 0 1 4 ⌊ tan − 1 x ⌋ d x = a − cot b , what is ⌊ b a ⌋ ?
Notation: ⌊ ⋅ ⌋ denotes the floor function .
Please post your solution.
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In the expression tan1, 1 is in radians. So while changing tan in to cot, it should be cot(pi/2 - 1) which will leave us with 'b' as 8/14.
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Oh sorry for that just wanted to make this problem a Level 2
Yes with that answer comes 3528
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Can you help me how to change the answer @Krishna Sharma @Somdutt Goyal
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@U Z – I guess only moderator and staff can change
@U Z – I have updated the answer to 3528, and reverted the change you made to the problem.
To get the answer updated, you can report your problem as having a wrong answer, and specify what you want to correct it to (and why).
Note that tan − 1 x is an increasing function for x ∈ [ 0 , 2 0 1 4 ] and that tan − 1 2 0 1 4 ≈ 1 . 5 7 0 . Then we have:
I = ∫ 0 2 0 1 4 ⌊ tan − 1 x ⌋ d x = ∫ 0 tan 1 ⌊ tan − 1 x ⌋ d x + ∫ tan 1 2 0 1 4 ⌊ tan − 1 x ⌋ d x = 0 + ∫ tan 1 2 0 1 4 d x = 2 0 1 4 − tan 1 = 2 0 1 4 − cot ( 2 π − 1 )
Therefore, ⌊ b a ⌋ = ⌊ 2 π − 1 2 0 1 4 ⌋ = 3 5 2 8 .
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= ∫ 0 t a n 1 0 + ∫ t a n 1 2 0 1 4 1
= 2 0 1 4 − t a n 1