1 #ifndef STAN_MATH_REV_FUN_COS_HPP 2 #define STAN_MATH_REV_FUN_COS_HPP 3 4 #include <stan/math/prim/fun/abs.hpp> 5 #include <stan/math/prim/fun/cos.hpp> 6 #include <stan/math/prim/fun/isinf.hpp> 7 #include <stan/math/prim/fun/isfinite.hpp> 8 #include <stan/math/rev/core.hpp> 9 #include <stan/math/rev/meta.hpp> 10 #include <stan/math/rev/fun/abs.hpp> 11 #include <stan/math/rev/fun/cosh.hpp> 12 #include <stan/math/rev/fun/sinh.hpp> 13 #include <cmath> 14 #include <complex> 15 16 namespace stan { 17 namespace math { 18 19 /** 20 * Return the cosine of a radian-scaled variable (cmath). 21 * 22 * The derivative is defined by 23 * 24 * \f$\frac{d}{dx} \cos x = - \sin x\f$. 25 * 26 * 27 \f[ 28 \mbox{cos}(x) = 29 \begin{cases} 30 \cos(x) & \mbox{if } -\infty\leq x \leq \infty \\[6pt] 31 \textrm{NaN} & \mbox{if } x = \textrm{NaN} 32 \end{cases} 33 \f] 34 35 \f[ 36 \frac{\partial\, \mbox{cos}(x)}{\partial x} = 37 \begin{cases} 38 -\sin(x) & \mbox{if } -\infty\leq x\leq \infty \\[6pt] 39 \textrm{NaN} & \mbox{if } x = \textrm{NaN} 40 \end{cases} 41 \f] 42 * 43 * @param a Variable for radians of angle. 44 * @return Cosine of variable. 45 */ cos(var a)46inline var cos(var a) { 47 return make_callback_var(std::cos(a.val()), [a](const auto& vi) mutable { 48 a.adj() -= vi.adj() * std::sin(a.val()); 49 }); 50 } 51 52 /** 53 * Return the cosine of a radian-scaled variable (cmath). 54 * 55 * 56 * @tparam Varmat a `var_value` with inner Eigen type 57 * @param a Variable for radians of angle. 58 * @return Cosine of variable. 59 */ 60 template <typename VarMat, require_var_matrix_t<VarMat>* = nullptr> cos(const VarMat & a)61inline auto cos(const VarMat& a) { 62 return make_callback_var( 63 a.val().array().cos().matrix(), [a](const auto& vi) mutable { 64 a.adj() -= vi.adj().cwiseProduct(a.val().array().sin().matrix()); 65 }); 66 } 67 /** 68 * Return the cosine of the complex argument. 69 * 70 * @param[in] z argument 71 * @return cosine of the argument 72 */ cos(const std::complex<var> & z)73inline std::complex<var> cos(const std::complex<var>& z) { 74 return stan::math::internal::complex_cos(z); 75 } 76 77 } // namespace math 78 } // namespace stan 79 #endif 80