*y*=

*f(x*) and

*y′*=

*F'(x*) are continuous on the closed interval [

*a, b*], then the arc length (

*L*) of

*f(x*) on [

*a,b*] is

Similarly, if *x* = *f(y*) and *x'* = *f'*( *y*) are continuous on the closed interval [ *a,b*], then the arc length ( *L*) of *f(y*) on [ *a,b*] is

**Example 1:** Find the arc length of the graph of

**Example 2:** Find the arc length of the graph of *f(x*) = ln (sin *x*) on the interval [π/4, π/2].