In the online description of math.h (http://www.arduino.cc/en/Math/H) the following comment regarding the Atmega8 chip is made:
The Atmega8 chip, which is now dated, but still supported, does not have enough memory to be able to use the math.h library so you will probably need to update to an Atmega168 if you wish to use any of these functions."
I have tested an Atmega8 chip on an UNO board by calling a couple of functions from the math library. The sketch basically reads in an analog pin, scale the value to a voltage and then uses Serial to print the values. I have added 4 functions from math to test what will happen, but everything appeared normal: x = 5.0000 log(x) = 1.6094 log10(x) = 0.6990 exp(x) = 148.4131 square(x) = 25.0000
No apparent problems (and the 4 math statements added 840 bytes to the sketch size), so I think the math.h web page should be modified so that it does not imply an Atmega8 cannot call these functions. I suggest that the quoted sentence gets changed to something more accurate such as:
The Atmega8 chip, which is now dated, but still supported, has little memory so care should be taken when calling math functions to not run into memory constraints.