The sphinx, a mythological creature with the body of a lion and the head of a man, symbolised the king and pharaonic power. The rearing cobra with its wings outstretched offers protection and this is echoed by the seated figure of Sekhmet. The goddess, as a warrior deity, was seen as the protector of pharaohs. Sekhmet was also associated with Ra and was thus a solar deity. All three signs are thus connected, offering the protection of the pharaoh and referencing the apotropaic properties of the sun.
To find out more about Ancient Egyptian amulets please see our relevant blog post: Egyptian Amulets and their Meanings.