Now that we have looked at the C form along with how to play the major pentatonic in that form, we will temporarily move away from C and go onto the next letter, A. (If this is your first visit, it may be helpful for you to refer to my first lesson on the CAGED method here)
As discussed, the open A chord is a Triad Chord. This of course means that it requires a root, 3rd, and a 5th. The diagram below draws out the location of the A chord:
Because E is one of the notes in an A chord, you can strum all 6 strings without compromising the sound, when played open. The number structure of an A form chord (we'll skip the low E string) is:
Or you can repeat 1513 until you have the structure memorized. (Just so you know the actual notes played here are A, E, A, and C#). Later, I will briefly go over the major scale so you can figure out the notes of any scale on your own.
Moving up the neck of the guitar, pick a fret, and always remember to identify your roots! Since we now know that for an A form chord like C, the first root appears on the A string (second string). In the example below, we will play the D chord using the A form:
If you are having difficulty barring all three notes, try to practice slowly. If after practicing it still seems impossible, you can use your middle, ring, and pinky finger to play the bottom three notes on the chord. Try plucking each note one at a time and name that number. Finding the root is especially important. I can't stress that enough. Once you identified your roots, you are almost there. Remember the pattern and play that chord.
Try going up and down the neck. Identify the roots and their corresponding letter names. Challenge yourself some more and try to name the notes of the 3rds and 5ths. I hope you are starting to notice the pattern here.