Bad math when using * operator along with Math.pow

From: webmaster_at_nahnet.com ((webmaster_at_nahnet.com))
Date: 08/14/04 

Date: Sat, 14 Aug 2004 00:19:06 -0700

Check out this code. I need to be able to multiply a 15 digit decimal number by 10 to the power of 15, and come up with the correct answer. Easy enough for other languages to do, but J# seems to choke on it. Here's the code.

private void button1_Click (Object sender, System.EventArgs e)
{
        double dblPi = 3.14159265358979;
        double dblTheta = 121;
        double value = System.Math.Sin( (dblTheta / 180) * dblPi );
        System.Console.Write(value);
        System.Console.Write("\n");
        System.Console.Write(Math.pow(10, 15) * value);

        // Should return 857167300702113
        // but instead returns 857167300702114
}

My best guess is that it has something to do with the * operator. My guess is that it does some kind of crazy rounding, but looking at the code it doesn't make sense really. I made sure that the original value comes out right, and it does, and I trust the Math.pow function to come out right as well, but the combination of it all fails.

I'm so puzzled. HELP!

- Nick

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