page39 Published January 20, 2019 at 1024 × 768 in 1/14-1/18/19 (Power Rule Applications) PhySP19-SS4.2.4– Here is part of that magic. At some point you have to agree that once the difference between two numbers is small enough (the ∆ gets small enough to turn into “lil d”. the two numbers essentially the same number (t1 = t2 = t).