function triangleArea(a,b,c){
    return (((b[0] - a[0])*(c[1] - a[1]))-((c[0] - a[0])*(b[1] - a[1])));
}
Get the area of a triangle spanned by the three given points. Note that the area will be negative if the points are not given in counter-clockwise order.
@static
@method area
@param  {Array} a
@param  {Array} b
@param  {Array} c
@return {Number}