Minor chord construction - A minor

The A minor triad follows the standard formula for all minor triads. This means you take the 1st, 3rd and 5th notes from the related natural minor scale (obviously in this case A natural minor).

So if you look at the notes in the A natural minor scale
A B C D E F G A

So from this scale the 1st, 3rd and 5th notes are A, C and E which gives you

5th string  open = A
4th string 2nd fret = E
3rd string 2nd fret = A
2nd string 1st fret = C
1st string open = E

As with the C Major scale last month, some notes are doubled. 

Once you know the notes in the triad then you can figure out where else on the guitar you can play the same chord. Like this.

6th string 5th fret = A (same note as the open 5th string)
5th string 7th fret = E
4th string 7th fret = A
3rd string 5th fret = C
2nd string 5th fret = E
1st string 5th fret = A

Which is the standard 'E' shape bar chord version of A minor.