∫ 0 2 π 2 0 1 7 tan x d x
If the closed form of the integral above can be represented as b a π csc ( m π l ) , where a , b , m , l ∈ Z + with g cd ( a , b ) = 1 , g cd ( m , l ) = 1 and l is odd integer also l < m Find a + b + l + m .
Bonus : Generalize for ∫ 0 2 π n tan x d x .
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Ya the best way is with Beta Function.
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Yes Using beta functions is good way..But one can also use Contour integration to show that ∫ ( x m / ( 1 + x n ) d x = π / n c o s e c ( m + 1 ) π / n limits from 0-infinity
Yes, beta makes it very easy.
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Ya. How is this question? I made it by myself. :)
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Its great....keep posting !!! :)
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@A Former Brilliant Member – Why your age is showing 14?
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@Md Zuhair – My age is 17
Is there a solution without beta function?
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Yes , I think you can use integration by parts.
@A E Yes I tried but I couldnt do it. Can you give a rough sketches on how it's done?
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Using the Beta function:
∫ 0 2 π sin n 1 ( x ) cos n − 1 ( x ) d x = 2 1 β ( 2 n n + 1 , 2 n n − 1 ) = 2 Γ ( 2 n n + 1 + n − 1 ) Γ ( 2 n n + 1 ) Γ ( 2 n n − 1 )
Using Euler's Reflection Formula: Γ ( x ) Γ ( 1 − x ) = sin ( π x ) π
∫ 0 2 π sin n 1 ( x ) cos n − 1 ( x ) d x = 2 Γ ( 2 n 1 + 2 1 ) Γ ( 2 1 − 2 n 1 ) = 2 sin ( π ( 2 n 1 + 2 1 ) ) π
Sub in n = 2017 for 2 sin ( 2 0 1 7 1 0 0 9 π ) π