①(1-x)/(9-4x^2)^(1\2)=1\2(9\4-x^2)^(1\2)
-4x/4(9-4x^2)^(1\2)
∴∫（1-x）/√9-4x² dx
=(1/2)*arcsin(2x/3)+(1/4)*(9-4x^2)^(1/2)+C
②设x=3sect 0