The equation above holds true for positive integers , and , where is as large as possible and co-prime to and . Find the minimum value of .
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The integration ∫ 0 1 0 1 0 2 4 π sin 6 4 x d x can be simplified to ∫ 0 2 π sin 8 x d x . Before to integrate let us generalize the integration of ∫ 0 2 π sin n x d x for any integer. n ≥ 1 .
∫ 0 2 π sin n x d x = ∫ 0 2 π sin n . sin n − 1 x d x ∫ 0 2 π sin n x d x = − cosx . sin n − 1 x d x ∣ 0 2 π + ( n − 1 ) ∫ 0 2 π cos 2 x . sin n − 2 x d x c c c c c Integration by parts ∫ 0 2 π sin n x d x = 0 + ( n − 1 ) ∫ 0 2 π cos 2 x . sin n − 2 x d x ∫ 0 2 π sin n x d x = ( n − 1 ) ∫ 0 2 π sin n − 2 x d x − ( n − 1 ) ∫ 0 2 π sin n x d x ∫ 0 2 π sin n x d x = n n − 1 ∫ 0 2 π sin n − 2 x d x ⟹ I = n n − 1 I n − 2 = n n − 2 . n − 1 n − 3 I n − 4 = n n − 1 . n − 2 n − 3 . n − 4 n − 5 I n − 6 = ⋯ Now integrating continuesly using Integration by parts till sin ∘ x if n is an even number and sinx d x if n is odd number we obtained as ∫ 0 2 π sin n d x = { n n − 1 . n − 2 n − 3 . n − 4 n − 5 ⋯ 2 π c c c c if n is even n n − 1 . n − 2 n − 3 . n − 4 n − 5 ⋯ 1 c c c c if n > 1 is odd Since in the case we find n = 8 an even number so ∫ 0 2 π sin 8 x d x = 2 . 4 . 6 . 8 7 . 5 . 3 . 1 π = 3 2 ( 4 ! ) 1 0 5 . Hence the value of a + b + c = 1 0 5 + 3 2 + 4 = 1 4 1 .