Is It a Right Triangle?

// Turned a math practice problem into a program.
// triangles holds an array of arrays of points, each
// of which defines a triangle. The program finds out
// whether or not those are right triangles.
// I decided to write this program because doing it
// by hand was boring and I was bored. Hey, who says
// nodejs has to be just for web apps / servers? Works
// fine for a scripting language too!
var inverse = num => 1 / num;
var slope = (p1, p2) => (p1.y - p2.y) / (p1.x - p2.x);
function right(p1, p2, p3){
    // call node with flag '--harmony-destructuring' to enable this
    var [ s1, s2, s3 ] = [ slope(p1, p2), slope(p1, p3), slope(p2, p3) ];
    return s1 == inverse(s2) || s1 == inverse(s3) || s2 == inverse(s3);
}

var triangles = [
    [
        {x:0, y:7},
        {x:-4, y:-2},
        {x:5, y:2}
    ],
    [
        {x:5, y:5},
        {x:5*Math.sqrt(3), y:-5*Math.sqrt(3)},
        {x:-5, y:-5}
    ],
    [
        {x:4, y:5},
        {x:-4, y:-1},
        {x:2, y:-9}
    ],
    [
        {x:8, y:6},
        {x:4, y:4},
        {x:-1, y:10}
    ]
];

console.log(triangles.map(
function(set){
    return "Is a right triangle? " + right(set[0], set[1], set[2]);
}));