The Earth's orbit has a radius of 1.52·1011 m, and that of Mercury has a radius of 6.98·1010 m. Consider these two orbits to be perfect circles (though in reality they are ellipses with slight eccentricity).
a) What is the length of a vector from Earth to Mercury (take the direction from Earth to Sun to be 0°) when Mercury is at the maximum angular separation in the sky relative to the Sun.
b) What is the direction of a vector from Earth to Mercury (take the direction from Earth to Sun to be 0°) when Mercury is at the maximum angular separation in the sky relative to the Sun.