demonstrate vs expound

demonstrate

verb
  • to show how to use (something). 

  • to show, display, or present; to prove or make evident 

  • to show the steps taken to create a logical argument or equation. 

  • to participate in or organize a demonstration. 

expound

verb
  • To set out the meaning of; to explain or discuss at length 

  • To make a statement, especially at length. 

How often have the words demonstrate and expound occurred in a corpus of books? (source: Google Ngram Viewer )