Question 148413
<pre><font size = 4 color = "indigo"><b>
{{{A=1/2}}}{{{abs(matrix(3,3,a,b,1,c,d,1,e,f,1))}}}

That's the formula for the area of a triangle whose
vertices are (a,b), (c,d), and (e,f) going around the
triangle counter-clockwise.

Example:

Suppose we want to find the area of the triangle whose
vertices are (4,3), (-5,7), (3,-6).   Those are in
counter-clockwise order.

{{{drawing(400,400,-8,8,-8,8, grid(1),
triangle(4,3,-5,7,3,-6)   )}}}

We just plug those corner points into the formula:

{{{A=1/2}}}{{{abs(matrix(3,3,4,3,1,-5,7,1,3,-6,1))=(1/2)85= 42.5}}}

Edwin</pre>