∫ dx/sqrt(a^2-x^2)=arcsin(x/a)+C
sqrt(7-2x^2)=sqrt(2)*sqrt((7/2)-x^2)
∫ sqrt(2)dx/(sqrt(2)*sqrt((7/2)-x^2))= ∫dx/sqrt((7/2)-x^2)=
=arcsin(x/sqrt(7/2))+C=
=arcsin(sqrt(2)x/sqrt(7))+C
или так:
2x^2=u^2
u=sqrt(2)x
du=sqrt(2)dx
∫ du/sqrt(7-u^2)=arcsin(u/sqrt(7))+C=arcsin(sqrt(2)x/sqrt(7))+C