Triangle Area Side Side Side Given three sides of a triangle, print area of this triangle.
Test cases:
In: 2,3,4
Out: 2.90473750965556
In: 3,4,5
Out: 6
Given the sides \$a\$, \$b\$, and \$c\$, you can assume that \$a&gt;0\$, \$b&gt;0\$, \$c&gt;0\$, \$a+b&gt;c\$, \$b+c&gt;a\$, and \$c+a&gt;b\$.
This is code-golf, shortest answer per language in bytes wins.
J, 23 19 chars

   (4%~2%:[:*/+/-0,+:)

   (4%~2%:[:*/+/-0,+:) 2 3 4
2.90474

   (4%~2%:[:*/+/-0,+:) 3,4,5
6


17-char version if input is in i: 4%~%:*/(+/,+/-+:)i

original 23-char version: (%:@(+/**/@(+/-+:))%4:)