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 Let n\geq 2 be a natural numberr and 0<\Theta <\pi/2

Then  \int \frac{(sin^{n}\Theta -sin\Theta )^{1/n}\cos\Theta }{\sin^{n+1}\Theta}d\Theta          is equal to: (where C is a constant of integration)

  • Option 1)

    \frac{n }{n^{2}-1}(1-\frac{1}{sin^{n-1}\theta})^{n+1/n}+C

     

  • Option 2)

    \frac{n}{n^{2}+1}(1-\frac{1 }{\sin^{n-1}\Theta})^{n+1/n} +C

     

     

  • Option 3)

     

    n/n^{2}-1(1+1/sin^{n-1}\Theta )^{n+1/n}+c

  • Option 4)

     

    \frac{n}{n^{2}-1}(1-\frac{1}{\sin^{n+1}\Theta })^{n+1/n}+C

Answers (1)

best_answer

 

Integration by substitution -

The functions when on substitution of the variable of integration to some quantity gives any one of standard formulas.

 

 

- wherein

Since \int f(x)dx=\int f(t)dt=\int f(\theta )d\theta all variables must be converted into single variable ,\left ( t\, or\ \theta \right )

 

 

 

Indefinite integrals for Algebraic functions -

 \frac{\mathrm{d}}{\mathrm{d} x} \frac{\left ( x^{n+1} \right )}{n+1}=x^{n} so \int x^{n}dx=\frac{x^{n+1}}{n+1}

- wherein

Where  n\neq-1

 

\int \frac{(\sin ^{n}\theta -\sin \theta )^{\frac{1}{n}}\cos \theta }{\sin ^{n+1}\theta }d\theta

This can be written as 

\int \frac{\sin \theta (1-\frac{1}{\sin ^{n-1}\theta })^{\frac{1}{n}}}{\sin ^{n+1}\theta \sec \theta }d\theta

put 1-\frac{1}{\sin ^{n-1}\theta }=t

\frac{n-1}{\sin ^{n}\theta }\cos \theta \: \: d\theta =dt

Now,

\frac{1}{n-1}\int (t)^{}\frac{1}{n}dt=\frac{1}{n-1}\frac{(t)^{\frac{1}{n}+1}}{\frac{1}{n}+1}+C

                               =\frac{1}{n-1}\frac{t^{(\frac{1}{n}+1)}}{\frac{1}{n}+1}+C

                              =\frac{1}{n-1}(1-\frac{1}{\sin ^{n-1}\theta })^{\frac{1}{n}+1}+C 


Option 1)

\frac{n }{n^{2}-1}(1-\frac{1}{sin^{n-1}\theta})^{n+1/n}+C

 

Option 2)

\frac{n}{n^{2}+1}(1-\frac{1 }{\sin^{n-1}\Theta})^{n+1/n} +C

 

 

Option 3)

 

n/n^{2}-1(1+1/sin^{n-1}\Theta )^{n+1/n}+c

Option 4)

 

\frac{n}{n^{2}-1}(1-\frac{1}{\sin^{n+1}\Theta })^{n+1/n}+C

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