This math teacher is excellent in teaching the students to memorize minimum. His example is integrate secant. Most textbooks use a trick ie multiply (sec + tan) above and below, then by substitution. He goes by first principle, change sec = 1/cos, then try to use 2 common trigo sine and cosine, he multiplies cos above & below to make: sec = cos / 1-sin^2,… then integrate by part…
Mathtuition88 