1 #ifndef STAN_MATH_FWD_SCAL_FUN_ACOSH_HPP 2 #define STAN_MATH_FWD_SCAL_FUN_ACOSH_HPP 3 4 #include <stan/math/fwd/core.hpp> 5 #include <stan/math/prim/scal/fun/square.hpp> 6 #include <cmath> 7 8 namespace stan { 9 namespace math { 10 11 template <typename T> acosh(const fvar<T> & x)12inline fvar<T> acosh(const fvar<T>& x) { 13 using std::sqrt; 14 return fvar<T>(acosh(x.val_), x.d_ / sqrt(square(x.val_) - 1)); 15 } 16 17 } // namespace math 18 } // namespace stan 19 #endif 20