m.41-51: E-flat Major IV, I64V7, I, V42, I6, IV6 Fr.6, V, V42, V65/IV, IV V7, I
In the measure 46 on the first and second beat Beethoven wrote nice IV4 chord followed by Fr.6. Voicing is peaty good (key board style), in the bass is C which goes to the C flat, half step down. In the right hand we have E flat A Flat, goes to the E flat F and A natural. In measure 47 we have nice resolution V chord(C flat to the B flat, A natural to the B flat contrary emotion, E flat to the D and F stays) which is nice Half Cadence ( good mode mixture).
In measure 49-50 chord is V65/IV not a augmented-sixth chord. Beethoven didn't use the augmented-sixth chord because V65/IV sounds much stronger and stable than augmented-sixth chord "mixture chord". Also he didn't use augmented-sixth chord second time because of the cadence IV V I PAC.
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