How do I get arctan MATH function in iphone SDK?
The function you are looking for is atan(double)
Use the "2nd"-function under the "("-key, top left with the iphone in horizontal position. The tan key will change to tan-1, i.e. arctan.
来源：https://stackoverflow.com/questions/5339595/how-do-i-get-arctan-math-function-in-ios