I think of it in terms of the relationships regarding circle of 5th's.
C scale = C Dm Em F G Am Bdim
Fifth = G Amaj Bmaj C Dmaj Emaj F#maj
The 2 chords you mention are a 5th away from the C scale. Amaj is the "5 of 2" in the C harmonized scale.
Last edited by limestone; 03/27/23 04:13 PM.