1 #ifndef STAN_MATH_FWD_SCAL_FUN_INV_SQUARE_HPP 2 #define STAN_MATH_FWD_SCAL_FUN_INV_SQUARE_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_square(const fvar<T> & x)12inline fvar<T> inv_square(const fvar<T>& x) { 13 T square_x(square(x.val_)); 14 return fvar<T>(1 / square_x, -2 * x.d_ / (square_x * x.val_)); 15 } 16 } // namespace math 17 } // namespace stan 18 #endif 19