¯ ¯
̠
­ - , , , . .
. , ­ - .
­ - , , . ­ .
: .

a b
c


: , b, - ,
.: S - , :
: > 0, b > 0, > 0, =? <>
a < b +c, b < a + c, c < a + b. b =? <b>
=? <>


= <S>
S =

= ( + b + )/2
: ­ , .