用各种等价代换代替旧很快出来了
tanx - sinx = sinx [1/cosx -1] =sinx (1-cosx)/cosx ~ x * 2(x/2)^2 = x^3/2
arctan3x ~ 3x
e^x-1 ~ x
1-根号(1+x) ~ 1- (1+x/2) =-x/2
ln(1+2x) ~ x
带入后得到
x^3/2 * 3x * x /(x/2 * x) =3x^3
答案为C
用各种等价代换代替旧很快出来了
tanx - sinx = sinx [1/cosx -1] =sinx (1-cosx)/cosx ~ x * 2(x/2)^2 = x^3/2
arctan3x ~ 3x
e^x-1 ~ x
1-根号(1+x) ~ 1- (1+x/2) =-x/2
ln(1+2x) ~ x
带入后得到
x^3/2 * 3x * x /(x/2 * x) =3x^3
答案为C