3. Решить уравнение arcsin(x)+arcsin(x/2)=pi/4

$arcsin(x)+arcsin( \frac{x}{2})= \frac{ \pi}{4}$
$x=sin(a); x/2=sin(b);$
$\left \{ {{a+b= \frac{ \pi}{4} } \atop {sin(a)=2*sin(b)}} \right.$
$sin(a)=2sin(\frac{ \pi }{4}-a)$
$sin(a)= \sqrt{2}(cos(a)-sin(a)$ )
$\frac{1}{ \sqrt{2} } =ctg(x)-1$
$ctg(a)= \frac{\sqrt{2}-2 }{2}$
$\frac{ +-\sqrt{1- x^{2}} }{x} = \frac{\sqrt{2}-2 }{2}$
$4-4 x^{2} =6 x^{2} -4 \sqrt{2} x^{2}$
$x^{2} = \frac{4}{10-4 \sqrt{2} }$
$x = +- \sqrt{\frac{4}{10-4 \sqrt{2} } }$