β \beta -day Problem 2

Calculus Level 4

The integral 0 1 1 x 2 ( 1 x ) 3 d x \int^1_0\frac{1}{\sqrt[3]{x^2(1-x)}}dx can be written as a π b \frac{a\pi}{\sqrt{b}}

Find a + b a+b

The theme might have given you the hint .


The answer is 5.

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2 solutions

Shriram Lokhande
Aug 6, 2014

We will use the following B ( x , y ) = 0 1 t x 1 ( 1 t ) y 1 d t B(x,y)=\int^1_0t^{x-1}(1-t)^{y-1}\,dt B ( x , y ) = Γ ( x ) Γ ( y ) Γ ( x + y ) B(x,y)=\frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)} Γ ( x ) Γ ( 1 x ) = π sin ( π x ) \Gamma(x)\Gamma(1-x)=\frac{\pi}{\sin(\pi x)} The integral I = 0 1 1 x 2 ( 1 x 3 d x = 0 1 x 2 3 ( 1 x ) 1 3 d x I=\int^1_0\frac{1}{\sqrt[3]{x^2(1-x}}\,dx=\int_0^1x^{-\frac{2}{3}}(1-x)^{-\frac{1}{3}}dx I = 0 1 x 1 3 1 ( 1 x ) 2 3 1 d x \Rightarrow I=\int_0^1x^{\frac{1}{3}-1}(1-x)^{\frac{2}{3}-1}\,dx I = B ( 1 3 , 2 3 ) = Γ ( 1 3 Γ ( 2 3 ) Γ ( 1 ) I=B(\frac{1}{3},\frac{2}{3})=\frac{\Gamma(\frac{1}{3}\Gamma(\frac{2}{3})}{\Gamma(1)} I = Γ ( 1 3 ) Γ ( 1 2 3 ) = π s i n ( π 3 ) = 2 π 3 I=\Gamma(\frac{1}{3})\Gamma(1-\frac{2}{3})=\frac{\pi}{sin(\frac{\pi}{3})}=\frac{2\pi}{\sqrt{3}} Hence , we get our answer as a + b = 5 a+b=\boxed{5}

Same as done. Here is an upvote

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