Why does calculator say that $\sqrt{4} = 2$?

Question

Possible Duplicate:
Square roots — positive and negative

I know that the square roots of four are

• 2 because $2^2=4$
• and $-2$ because $(-2)^2=4$

Are there any conventions in considering primarily the positive square root or adding the $\pm$ symbol in the calculator screen would be a cost factor?

Answer 1

The very same question could also apply to other functions (e.g. trigonometric functions). SQRT is defined as returning only the +ve value of the square root. Check here for a thorough discussion on this topic: http://forums.randi.org/archive/index.php/t-36241.html.