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