function areaTriangle(a,b,c) {
    let area, perimeter;

    perimeter = (a + b + c)/2;
    //heron's formula
    area = Math.sqrt(perimeter * ((perimeter - a)  * (perimeter - b) * (perimeter = c)));

    return area;
}

//areaTriangle(3,3,9) perimeter returns 9(arg of c). Should be 7.5.