Question 452338
<pre>
What you want is the length of the green arc in the figure below

{{{drawing(400,1000/3,-1.5,1.5,-2,.5,

green(arc(0,-sqrt(3),4,-4,60,120)),
line(-1,0,1,0), locate(0,0,180m),
red(line(1,0,0,-sqrt(3)), line(-1,0,0,-sqrt(3))),
locate(-.06,-1.4,"60°")

 )}}}

The formula is s = &#5054;r, where &#5054; is measured in radians.
We can convert &#5054; to radians but we need the length of the
radii ("radiuses" if you prefer) which are the two red lines. 
But the radii are equal in length making the triangle 
isosceles.  But an isosceles triangle with a 60° internal angle
is an equilateral triangle and all three sides are 180m. That
means the two red line segments are equal in length to 
the black line so the radius r, is 180m.

Before we substitute into this formula we must convert 60° to
radians by multiplying it by <font face = "symbol">p</font>/180°

60°(<font face = "symbol">p</font>/180°) = <font face = "symbol">p</font>/3.

s = &#5054;r
s = (<font face = "symbol">p</font>/3)(180m) 
s = (3.14/3)(180m)

Now use your calculator to get

s = 188.4m

Edwin</pre>