Question 519269
<pre> You forgot to give the measure of the central angle
of the arc C, so I arbitrarily selected 70°.  You can redo
it using the measure you were given that you forgot to give 
here.

{{{drawing(400,400,-1,1,-1,1,

circle(0,0,1), line(0,0,cos(40*pi/180),sin(40*pi/180)),
line(0,0,cos(-30*pi/180),sin(-30*pi/180)),locate(.1,.06,"70°"),
green(arc(0,0,.6,-.6,330,400)), red(locate(1,.3,C)),
locate(.4,-.15,3cm), locate(.4,.35,3cm),

arc(0,0,2,-2,40,330), red(arc(0,0,2,-2,330,400))

 )}}} 


Set up the proportion:

                 {{{"arc_length"/
"central_angle"}}} = {{{circumference/"360°"}}} 

Since circumference = 2{{{pi}}}Śradius

                 {{{"arc_length"/
"central_angle"}}} = {{{(2pi*radius)/"360°"}}}


                 {{{C/
"70°"}}} = {{{(2pi*3)/"360°"}}}

                 {{{C/
"70°"}}} = {{{(2pi*3)/"360°"}}}

                 {{{C/
"70°"}}} = {{{(2pi*3)/"360°"}}}

                 {{{C/
"70°"}}} = {{{(6pi)/"360°"}}}

                 {{{C/
"70°"}}} = {{{(pi)/"60°"}}}


                 C = {{{("70°"*pi)/"60°"}}}

                 C = {{{expr(7/6)pi}}}

Edwin</pre>