var i,j;
i = 0, j = 0;
for (i = 1; i <= 9; i++) {
for (j = 1; j <= i; j++) {
document.write(j + "*" + i + "=" + i * j + " ");
}
document.write("<br/>");
}
var a, b, c;
function sum(a, b,) {
var s = ((parseInt(a.value) + parseInt(b.value)) * (parseInt(c.value))) / 2;
alert("梯形的面积是：" + s);
}
</script>
<form>
上底<input type="text" name="a"><br />
下底<input type="text" name="b"><br />
高度<input type="text" name="c"><br />
<input type="button" onclick="sum(a,b,c)" value="求面积">
