acos

Overview

As explained in Chapter 8, both C and C++ originally supported the same set of 22 math functions. However, as C++ matured, it added overloaded versions of these original functions. Then, C99 greatly increased the size of the C math library in ways that C++ does not support. The net result of these changes is that today, the C and C++ math libraries have diverged, although both still support the original core set of math functions. Because of the differences between C and C++ in this area, the C math functions (including those added by C99) are described in Chapter 8. This chapter describes the math functions defined by C++.

In C++, the math functions require the header <cmath>. In addition to declaring the math functions, this header defines the macro called HUGE_VAL. The macros EDOM and ERANGE are also used by the math functions. These macros are defined in the header <cerrno>. If an argument to a math function is not in the domain for which it is defined, an implementation-defined value is returned, and the built-in global integer variable errno is set equal to EDOM. If a routine produces a result that is too large to be represented, an overflow occurs. This causes the routine to return HUGE_VAL, and errno is set to ERANGE, indicating a range error. If an underflow happens, the function returns zero and sets errno to ERANGE.

C++ supports the original math functions defined by C89. However, in C89, these functions operate only on floating-point values of type double. To these functions, C++ adds overloaded versions that explicitly accommodate values of type float and long double. The operation of the functions is otherwise unchanged.

All angles are in radians.