Question 734028
The radius of a circle is {{{r=5km}}}. 

the area of a sector bounded by a {{{180}}}° arc is equal {{{1/2}}} of area of the full circle or equal to a semicircle area

{{{A=(1/2)r^2*pi)}}}

{{{A=(1/2)(5km)^2*pi)}}}

{{{A=(1/2)25*pi*km^2)}}}

{{{A=12.5*pi*km^2)}}}