"It's not rational to treat 2+2 as 5." — logical as contrasted to illogical
"I know you're upset, but please think about this in a rational manner." — based on reason as contrasted to emotion
"When I was 10-years-old, I wasn't very smart, but I was still rational." — capable of using reason as contrasted to being insane or lacking the ability to reason
"In matters of the heart, I trust my intuition more than my rational analysis." — based on a logical analysis as contrasted to intuition, instinct, custom, tarot-card reading, or some other system of decision making
Even though I am not yet a member of the board, I was able to meet with Superintendent Seymour—who has, I assure you, my deepest respect—and discuss in a calm, rational fashion what might be done.
There are no more uses of "rational" in Nothing but the Truth.