S ( \\ displaystyle s ) is half the perimeter b ( \\ displaystyle b ) and c ( \\ displaystyle c ) are the length of each side .
Half the perimeter is a ( \\ displaystyle a ) .
s ( \\ displaystyle s ) is half the perimeter , a ( \\ displaystyle a ) , b ( \\ displaystyle b ) and c ( \\ displaystyle c ) are the length of each side .