Why is “mira” made to match with tú?

Question

"mira (tú) qué bien", "mire (usted) qué bien"I don’t understand why “mira” is made to match with “tú” and “mire” with “Usted”. Shouldn’t “Usted” match both?

Accepted Answer

Hola Alejandro,
These are using the imperative for tú and usted. They're not the same form. 
The imperative affirmative of tú is "mira" and the imperative affirmative of usted is "mire", the latter being the same form as the present subjunctive. 
Here are two lessons that will help:
Forming the imperative of tú for most verbs (affirmative commands)
Forming the imperative for usted/ustedes/nosotros/nosotras (affirmative and negative commands)
Saludos
Inma

Answer

Hola Alejandro,

Usted will match "mira" in the present tense but this changes to "mire" in the imperative, while Tú changes to "mira" in the imperative [drop the s]. You may be confusing the present and imperative conjugations.

I hope that helps. Saludos. J