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32) Integrate the functions  \frac{1}{1+ \cot x }

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Given function  \frac{1}{1+ \cot x }

Assume that I = \int \frac{1}{1+ \cot x } dx

 Now solving the assumed integral;

I = \int \frac{1}{1+ \frac{\cos x }{\sin x} } dx

= \int \frac{\sin x }{\sin x + \cos x } dx

= \frac{1}{2}\int \frac{2\sin x }{\sin x + \cos x } dx

= \frac{1}{2}\int \frac{(\sin x+ \cos x ) +(\sin x -\cos x ) }{(\sin x + \cos x) } dx

=\frac{1}{2}\int 1 dx + \frac{1}{2} \int \frac{\sin x -\cos x }{\sin x +\cos x } dx

=\frac{1}{2}(x) + \frac{1}{2} \int \frac{\sin x -\cos x }{\sin x +\cos x } dx

Now, to solve further we will assume \sin x + \cos x =t

Or, (\cos x -\sin x)dx =dt

\therefore I = \frac{x}{2}+ \frac{1}{2}\int \frac{-(dt)}{t}

= \frac{x}{2}- \frac{1}{2}\log|t| +C

Now, back substituting the value of t,

= \frac{x}{2}- \frac{1}{2}\log|\sin x + \cos x| +C 

 

Posted by

Divya Prakash Singh

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