How does connotation and denotation affect an author's purpose?
Connotation may reveal a persuasive purpose.
Denotation affects everything an author writes.
In order to answer this question, I must first be sure that you understand the terms.
Connotation is the feeling or impression given by a word.
Denotation is the accepted definition of the word.
An Author's Purpose can be to Inform, Persuade, or Entertain.
Though some people include Compare and Express as well.
Now let us begin.
A good author will decide what his/her purpose is and then use words with specific Connotations and Denotations to further that purpose.
An Author's Purpose should affect his word choice and by extension the Connotations and Denotations in his writing.
When this is true, readers can use critical thinking and logic to determine what the author is trying to accomplish through his/her writing.
But if his word choice is affecting his purpose, he probably never decided what he was writing until he had already written it.
I hope this serves you well, and I am sorry that most of my answer was contradicting your question.