or an object in equilibrium the sum of the torques acting on it vanishes only if each torque is calculated about: the point of application of the force the center of mass the center of gravity the geometrical center the same point

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.

c because the action was the roller coaster reaches bottom of hill (action) reaction would be blood tends to drain away from head

hope this !