<p><a href="https://play.golang.org/p/f6cREuQaAv">Here</a>.</p>
<p>Why does this equation returns NaN, when it should return −4,929420801 (according to my calculator).</p>
<hr/>**评论：**<br/><br/>ibishvintilli: <pre><p>Apparently the result should be a complex number and should be handled with the mapth/cmplx package.</p>
<p>fmt.Println(cmplx.Pow(-2910.579503363819, 0.2))</p>
<p>result was:
(3.987985200072245+2.897440848908454i)</p>
<p>The result was the same as in wolfram alpha:
<a href="https://www.wolframalpha.com/input/?i=(-2910.579503363819)%5E0.2" rel="nofollow">https://www.wolframalpha.com/input/?i=(-2910.579503363819)%5E0.2</a></p></pre>Swedophone: <pre><p>Actually Wolfram alpha lists all five 5th roots. One is "-4.9294208005523940 + 0.×10<sup>-16</sup> i".</p></pre>KillerMcFluffy: <pre><p>(-2910.579503363819) ^ .02 = 1.17063569 + 0.0736501551 i
according to Google </p>
<p>You're essentially taking the (50th) root of a negative number, so you get an imaginary answer...... math.Pow returns a float64 so it's NaN</p></pre>KillerMcFluffy: <pre><p>you are doing this: -(2910.579503363819<sup>0.2)</sup> = -4.92942080055
on your calculator</p></pre>kerakk19: <pre><p>I'm doing something like this: (-2910.579503363819)<sup>0.2</sup></p>
<p>And the result is: −4,929420801</p>
<p>And google shows: -4.9294208 <a href="https://www.google.pl/search?q=(-2910.579503363819)%5E0.2&oq=(-2910.579503363819)%5E0.2&aqs=chrome..69i57.2563j0j9&client=ubuntu&sourceid=chrome&ie=UTF-8" rel="nofollow">Link</a></p></pre>KillerMcFluffy: <pre><p>sorry, my bad! I copied wrong....
technically both -4.9294.... and (3.987...+2.8974...i) are 5th roots of -2910.579...</p>
<p>guessing that special case (that <a href="/u/davedev" rel="nofollow">/u/davedev</a> pointed out) exists because floating point math with fractional exponents isn't very precise, but not positive.</p></pre>markuspeloquin: <pre><p>.2 isn't representable with a base 2 floating point. The only way you can define exponentiation of a negative number to a non-integer is to convert the exponent to a rational number. If the exponent's denominator is positive, you get an imaginary number. But in base 2, denominators are <em>always</em> positive. Something like this can only be done via symbolic math.</p></pre>daveddev: <pre><p>It appears to be a special case.</p>
<p><a href="https://golang.org/pkg/math/#Pow" rel="nofollow">https://golang.org/pkg/math/#Pow</a></p></pre>_0dd1sh: <pre><p>This is correct. To quote the last special case -</p>
<blockquote>
<p>Pow(x, y) = NaN for finite x < 0 and finite non-integer y</p>
</blockquote>
<p>OP's x is less than zero, and his y is a non-integer.</p></pre>
