================================ Essential Functions (Docstrings) ================================ .. autofunction:: sympy.physics.vector.dynamicsymbols .. autofunction:: sympy.physics.vector.functions.dot .. autofunction:: sympy.physics.vector.functions.cross .. autofunction:: sympy.physics.vector.functions.outer .. autofunction:: sympy.physics.vector.functions.express .. autofunction:: sympy.physics.vector.functions.time_derivative