Given a non-negative real number $\alpha$, the number $\sqrt\alpha$ is defined to be the unique non-negative real number $\beta$ such that $\beta^2=\alpha$. Since $\sqrt{\alpha}\geq 0$ for all $\alpha\geq 0$, then for any real $\gamma$, it follows that $$\sqrt{\gamma^2}=\begin{cases}\gamma &amp; \gamma\geq 0\\-\gamma &amp; \gamma&lt;0,\end{cases}$$ that is, $$\sqrt{\gamma^2}=|\gamma|.$$

Proving square root of a square is the same as absolute value
I'm trying to modify JavaScript (jQuery, Google Maps v.3) to get the size of #mao_canvas only 80% of the screen height, but I can't undestand what to modify in tihs function. Can anyone help me with this?
The basic idea is to get 80% height of #map_canvas.

$(function(){
  $("#map_canvas").css("height",$(window).height() + 'px');
  initialize();
});

