- #1
- 838
- 4
Homework Statement
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx[/tex]
The attempt at a solution
I complete the square for the quadratic:
[tex]\sqrt{3x^2-6x+1}
\\=\sqrt{3(x^2-2x+\frac{1}{3})}
\\=\sqrt 3 \times \sqrt{(x-1)^2-\frac{2}{3}}[/tex]
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx
\\=\frac{1}{\sqrt 3}\int^4_3 \frac{1}{\sqrt{(x-1)^2-\frac{2}{3}}}\,.dx
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{\sqrt 3(x-1)}{\sqrt 2}\right]^{x=4}_{x=3}
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{3\sqrt 3}{\sqrt 2}-\cosh^{-1}\sqrt 6\right][/tex]
I already simplified it but it doesn't agree with the final answer:
[tex]\frac{1}{\sqrt 3}\ln \left(\frac{15+\sqrt {219}}{12+\sqrt {138}}\right)[/tex]
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx[/tex]
The attempt at a solution
I complete the square for the quadratic:
[tex]\sqrt{3x^2-6x+1}
\\=\sqrt{3(x^2-2x+\frac{1}{3})}
\\=\sqrt 3 \times \sqrt{(x-1)^2-\frac{2}{3}}[/tex]
[tex]\int^4_3 \frac{1}{\sqrt{3x^2-6x+1}}\,.dx
\\=\frac{1}{\sqrt 3}\int^4_3 \frac{1}{\sqrt{(x-1)^2-\frac{2}{3}}}\,.dx
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{\sqrt 3(x-1)}{\sqrt 2}\right]^{x=4}_{x=3}
\\=\frac{1}{\sqrt 3} \left[\cosh^{-1}\frac{3\sqrt 3}{\sqrt 2}-\cosh^{-1}\sqrt 6\right][/tex]
I already simplified it but it doesn't agree with the final answer:
[tex]\frac{1}{\sqrt 3}\ln \left(\frac{15+\sqrt {219}}{12+\sqrt {138}}\right)[/tex]