Multi-line equation in math environment

multiline-equation.tex

\begin{align*}
  \sigma&=(P(0)\times (1-\mu)^2+P(2)\times (-1-\mu)^2+P(5)\times (-4-\mu)^2\\
  &\qquad {} + P(10)\times (-9-\mu)^2+P(50)\times (-49-\mu)^2\\
  &\qquad {} + P(100)\times (-99-\mu)^2+P(500)\times (-499-\mu)^2\\
  &\qquad {} + P(1000)\times (-999-\mu)^2+P(10000)\times (-9999-\mu)^2\\
  &\qquad {} + P(100000)\times (-99999-\mu)^2\\
  &\qquad {} + P(1000000)\times (-999999-\mu)^2)^{1/2}\\[3px]
  &\approx 330.307\pagebreak
\end{align*}