Get vertex pair from fixture.

[duplex199126]

Hi everyone.
First of all - sorry for my English.
My problem:
What is the best way to get vertex pair that contains point. I have square fixture and i create RayCast that collide with it.
So i get point of collision this raycast and my fixture. But i need get the line which raycast collide.

How i can get point 1 and 2.
Now i do that, I create Linear equation https://en.wikipedia.org/wiki/Linear_equation for each vertex pair, than i try search where it is more or less satisfies the conditions - i dont like that. maybe exist more good variant or at least know more powerful algorithm to search is point on line or not, because that i use - It has a large error. Help me find it pls.

private Vector2 test(PolygonShape ps, Vector2 point, Vector2 normal) {

    float[] vertexColl = new float[ps.getVertexCount()];

    for(int i = 0; i < ps.getVertexCount()-1; i++){
        ps.getVertex(i, v1);
        ps.getVertex(i + 1, v2);
        vertexColl[i] = isPointOnLine(v1, v2, point);
    }

    ps.getVertex(0, v1);
    ps.getVertex(ps.getVertexCount() - 1, v2);
    vertexColl[vertexColl.length-1] = isPointOnLine(v1, v2, point);

    int minIndex = min(vertexColl);

    ps.getVertex(minIndex, v1);
    ps.getVertex(((minIndex + 1) < vertexColl.length) ? minIndex + 1 : 0, v2);

    return null;
}
private float isPointOnLine(Vector2 startLine, Vector2 endLine, Vector2 point){
    return Math.abs((point.x - startLine.x) * (endLine.y - startLine.y) - (point.y - startLine.y) * (endLine.x - startLine.x));
}

public int min(float[] array) {
    int minIndex = 0;
    for (int i = 1; i < array.length; i++) {
        if (array[i] < array[minIndex]) minIndex = i;
    }
    return minIndex;
}