Calculate power of a negative number

Question

I relatively new to C# and since Math.Pow(x,y) returns NaN for a negative number(read: not negative power), I want to know how to calculate result more efficiently. What I am do

Answer 1

Math.Pow(x,y) returns NaN for a negative number.

That's because arbitrary exponentiation is not defined for a negative base:

http://en.wikipedia.org/wiki/Exponentiation

when the base b is a positive real number, b to the n can be defined for all real and even complex exponents n via the exponential function

Now, exponentiation of negative numbers to get a real result is defined if the power is an integer, as in your case, but Pow will not calculate it for you. What you should do is:

• Suppose you want to know Pow(-2, 5)
• Give Pow the problem Pow(2, 5) instead.
• Look at the exponent; if it is an even number then you've got the right answer. If it is an odd number, then make the answer negative.

So in this case, Pow(2, 5) returns 32. The exponent 5 is odd, so make it -32, and you're done.