Question 368137
<pre>
The determinant formula:
The area of the triangle whose vertices are (x<sub>1</sub>,y<sub>1</sub>),(x<sub>2</sub>,y<sub>2</sub>), (x<sub>3</sub>,y<sub>3</sub>)
is given by this formula:

{{{Area=expr(1/2)abs((matrix(3,3,x[1],y[1],1,x[2],y[2],1,x[3],y[3],1)))}}}

You can put the points in in any order as long as you take the absolute value
of the determinant:
(-1,3) (-2,0) (4,1)
{{{Area=expr(1/2)abs((matrix(3,3,-1,3,1,-2,0,1,4,1,1)))}}}

Do you know how to expand (i.e., evaluate) a determinant? If not post again,
asking how. The value of the determinant is 17 so

{{{Area=expr(1/2)*abs(17) = 17/2=8&1/2}}}

Edwin</pre>