- #1
Telemachus
- 835
- 30
Homework Statement
The statement says: Calculate the next integrals using the adequate trigonometric substitution:
[tex]\displaystyle\int_{}^{}x^2\sqrt[ ]{x^2+3}dx[/tex]
Homework Equations
[tex]ch^2(t)-sh^2(t)=1\Rightarrow{ch(t)=\sqrt[ ]{1+sh^2(t)}}[/tex]
The Attempt at a Solution
[tex]x=\sqrt[ ]{3}sh(t)[/tex]
[tex]dx=\sqrt[ ]{3}ch(t)dt[/tex]
[tex]u=ch(t)[/tex]
[tex]du=sh(t)dt[/tex]
[tex]dv=ch(t)dt[/tex]
[tex]v=sh(t)[/tex]
[tex]\displaystyle\int_{}^{}ch^2(t)dt=ch(t)sh(t)-\displaystyle\int_{}^{}sh(t)sh(t)dt[/tex]
[tex]\displaystyle\int_{}^{}ch^2(t)dt=ch(t)sh(t)-\displaystyle\int_{}^{}sh^2(t)dt=ch(t)sh(t)-\displaystyle\int_{}^{}(ch^2(t)-1)dt[/tex]
[tex]*[/tex] [tex]\displaystyle\int_{}^{}ch^2(t)dt=\displaystyle\frac{1}{2}(ch(t)sh(t)+t)[/tex]
[tex]9\displaystyle\int_{}^{}sh^2(t)ch^2(t)dt=9(\displaystyle\frac{sh^2(t)}{2}ch(t)sh(t)+t)-\displaystyle\int_{}^{}(ch(t)sh(t)+t)sh(t)ch(t)dt=9(\displaystyle\frac{sh^2(t)}{2}ch(t)sh(t)+t)-\displaystyle\int_{}^{}ch(t)^2sh(t)^2dt-\displaystyle\int_{}^{}ch(t)sh(t)tdt[/tex]
Well, if you see an easier way of solving this let me know :P
Bye there!
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