inv_square.hpp

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#ifndef STAN_MATH_FWD_FUN_INV_SQUARE_HPP
#define STAN_MATH_FWD_FUN_INV_SQUARE_HPP
 
#include <stan/math/fwd/meta.hpp>
#include <stan/math/fwd/core.hpp>
#include <stan/math/prim/fun/square.hpp>
 
namespace stan {
namespace math {
 
template <typename T>
inline fvar<T> inv_square(const fvar<T>& x) {
  T square_x(square(x.val_));
  return fvar<T>(1 / square_x, -2 * x.d_ / (square_x * x.val_));
}
}  // namespace math
}  // namespace stan
#endif