But are you sure about it? Because normally math.h is to be avoided in embedded systems because of execution time and code size produced by it. Especially if you take under consideration that this function takes a double as argument. You could also take a look at the below reference, where the author presents a couple of fast algorithms to calculate the square root of an integer.
Sometimes you can 'cheat' and just store a look-up table ; ) It's fast but consumes ROM of course.
I once wanted to draw arbitrary circles on an LCD and given the dimensions of the LCD, my lookup
table was acceptable, because I knew that only circles or arcs up to a certain dimension could be drawn on the LCD.