"As "| sin(x) | <= 1", and "arctan(x)/x >= 0, " we have"
| (sin(1/sqrt(x)) arctan(x))/(x sqrt(ln(1+x))) | <= | arctan(x)/(x sqrt(ln(1+x))) |
= arctan(x)/(x sqrt(ln(1+x)))" (both arctan(x)/x and "sqrt(...) >= 0")"
= arctan(x)/(sqrt(x) sqrt(x^-1) x sqrt(ln(1+x)))
= arctan(x)/(sqrt(x) x sqrt(x^-1 ln(1+x)))