Where is the opening from coronary sinus to other two openings?

The opening of the coronary sinus is to the right atrium. The other two openings that are relevant to the coronary sinus are the superior vena cava and the inferior vena cava. The superior vena cava opens to the right atrium and the inferior vena cava opens to the right atrium. The coronary sinus joins with the right atrium near to where these other two openings are located.