Friday 14 June 2013

calculus - How to do this integral without the inverse hyperbolic tan



We have the integral $\displaystyle\int \dfrac{1}{x^2+4x+3} dx$. I figured out that with a substitution you can rewrite this as $ - \displaystyle \int \dfrac{1}{1-u^2} du$, which is $-\tanh^{-1}(u)$. However, I wonder if there's another way to do this integral without having to use the (in my opinion) obscure inverse hyperbolic trig functions.



Answer



You can apply parital fractions to this problem and then simply integrate fractions by logarithms.



$$\frac{1}{x^2+4x+3}=\frac{1}{2(x+1)}-\frac{1}{2(x+3)}$$


No comments:

Post a Comment

real analysis - How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$

How to find $\lim_{h\rightarrow 0}\frac{\sin(ha)}{h}$ without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...