Write a program that prompts the user to enter three points $($x$1,$ y$1),($x$2,$ y$2),($x$3,$ y$3)$ of a triangle and displays its area.

The formula for computing the area of a triangle is:

s $=($side$1+$ side$2+$ side$3)/2$

area $=$ square root of s$($s $-$ side$1)($s $-$ side$2)($s $-$ side$3)$