Find the area of a sector with radius r=25r = 25r=25 and central angle 180^\\circ.
frac6254pi\\frac{625}{4}\\pifrac6254pi
frac6252pi\\frac{625}{2}\\pifrac6252pi
frac6262pi\\frac{626}{2}\\pifrac6262pi
625pi625\\pi625pi