х=2sint ⇒ dx=2costdt
4-x^2=4-4sin^2t=4(1-sin^2t)=4cos^2t
sqrt(4-x^2)=sqrt(4cos^2t)=2cost
∫dx/(sqrt(4-x^2)*x^2)=∫2costdt/(2cost*4sin^2t)=
=(1/4)∫dt/sin^2t=(1/4)(-ctgt)+C
x=2sint ⇒ sint=(x/2)
cost=sqrt(1-sin^2t)=sqrt(1-(x/2)^2)=(1/2)sqrt(4-x^2)
ctgt=cost/sint=sqrt(4-x^2)/x
О т в е т. -sqrt(4-x^2)/(4x) + С