I live in Boston, which is at latitude 42 degrees North, longitude 70 degrees west.

a) I happen to know that on the spring equinox (roughly March 22), the sun is directly over the equator. So why it do I see it rising directly east (true east, not magnetic), even though the equator is far south of me?

b) Similarly, on the summer solstice (roughly June 22), the sun is directly over the Tropic of Cancer (latitude 23.5 degrees North). In fact, this is the furthest North the sun ever gets. So why do I see the sun rising roughly East-North-East (halfway between true East and true NorthEast), even though the Tropic of Cancer is also south of me?