คำศัพท์คณิตศาสตร์
P1.8. Often times books show a proof of Euler’s Identity by looking at the Taylor series expansion for sin(x) and cos(x), comparing it to the expansion for e^x and saying “Tada, it works!” Here the goal is to derive the Euler relation, assuming that we know a little bit about differential equations. Put another way, we don’t wat to just show that it happens to work, but that it must work. First, we consider the following differential equation which represents simple harmonic motion such as from a pendulum (small angles) or a spring: