var mathfal = new mathfal({
        identity:{
            id: "mathfal_container",
            canvasId: "mathfal_canvas"
        }
    });
    document.getElementById("mathfal_button").onclick = function(){
        var mathfalValue = mathfal.validate(document.getElementById("mathfal_input").value);
        if(mathfalValue){
                alert("求导计算正确");
        }else{
                alert("求导计算错误");
        }
    }