How to prove that $\int_0^1 \exp\left(\frac{4x\sqrt{1-x^2}}{\sqrt{8x^2+1}}\right)\sqrt{\frac{1-8x^2+16x^4}{1+7x^2-8x^4}}dx=e-1$ show that

$$\int\limits_0^1 {\exp \left( {\frac{{4x\sqrt {1 - {x^2}} }}{{\sqrt {8{x^2} + 1} }}} \right)} \sqrt {\frac{{1 - 8{x^2} + 16{x^4}}}{{1 + 7{x^2} - 8{x^4}}}} dx = e - 1$$

I think this is nice integral,This problem is my china frend give me do it at yesterday, But I can't prove it. Thank you 
my try:let 
$$u=\dfrac{4x\sqrt{1-x^2}}{\sqrt{8x^2+1}}$$
then $$du=-\dfrac{4(8x^4+2x^2-1)}{\sqrt{1-x^2}(8x^2+1)^{\frac{3}{2}}}$$
 A: Let us note that  under the change of variables $y=\sqrt{\frac{1-x^2}{1+8x^2}}$ we have  $x=\sqrt{\frac{1-y^2}{1+8y^2}}$ and the interval $(0,\frac12)$ is mapped to $(\frac12,1)$ and vice versa. Also,
$$\frac{1-4x^2}{\sqrt{(1-x^2)(1+8x^2)}}dx=\frac{3(4y^2-1)dy}{(1+8y^2)\sqrt{(1-y^2)(1+8y^2)}}$$
Now our integral can be written as
\begin{align}
&\int_0^1e^{4xy}\frac{|1-4x^2|}{\sqrt{(1-x^2)(1+8x^2)}}dx=\\
=&\int_0^{\frac12}e^{4xy}\frac{1-4x^2}{\sqrt{(1-x^2)(1+8x^2)}}dx+\int_{\frac12}^1e^{4xy}\frac{4x^2-1}{\sqrt{(1-x^2)(1+8x^2)}}dx=\\
=&\int_0^{\frac12}e^{4xy}\frac{1-4x^2}{\sqrt{(1-x^2)(1+8x^2)}}dx+\int_0^{\frac12}e^{4xy}\frac{3(1-4y^2)}{(1+8y^2)\sqrt{(1-y^2)(1+8y^2)}}dy=\\
=&\int_0^{\frac12}e^{4xy}\frac{1-4x^2}{\sqrt{(1-x^2)(1+8x^2)}}dx+\int_0^{\frac12}e^{4xy}\frac{3(1-4x^2)}{(1+8x^2)\sqrt{(1-x^2)(1+8x^2)}}dx=\\
=&\int_0^{\frac12}e^{4xy}\frac{4(1-4x^2)(1+2x^2)}{(1+8x^2)\sqrt{(1-x^2)(1+8x^2)}}dx=\\
=&\int_0^{\frac12}e^{4xy}(4xy)'_xdx=\\
=&\left[\exp 4x\sqrt{\frac{1-x^2}{1+8x^2}}\,\right]_{0}^{\frac12}=\\
=&e-1.
\end{align}
