This arithmetic predicate calculates the arc tangent of the argument. This predicate is defined the ISO Prolog standard, acos/1 and asin/1 are not in the ISO Prolog standard.
see also: acos/1 asin/1 arithmetic in Prolog cos/1 cosh/1 is/2 sin/1 tan/1 tanh/1
| Examples | |
| X is atan(2.71). | succeeds, X is 1.217293 |
| X is atan(-0.1). | succeeds, X is -0.09966865 |
| Exceptions | |
| The floating point argument or result exceeds the floating point range | an evaluation_error(float_overflow) exception is thrown |
| The integer argument result exceeds the integer range | an evaluation_error(int_overflow) exception is thrown |