what quote and page number does it tell you atticus is smart?

There is a difference between being smart and wise, Atticus is both. The fact that Atticus is an effective lawyer in Maycomb tells us he is smart. I'll give you a quote for both:

Wise:

“Courage is not a man with a gun in his hand. It's knowing you're licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do.” (pg. 149 my copy)

Smart, Tom Robinson: "I can't use my left hand at all. I got it caught in a cotton gin when I was twelve years old. "

Atticus proves that Tom couldn't have raped Mayella.