Most differential equations textbooks fall into two categories: the highly theoretical (aimed at math majors) and the overly simplistic (aimed at general education). Spiegel’s Applied Differential Equations occupies a rare middle ground. It was written specifically for engineering, physics, and applied science students who need to use DEs, not just prove them.
You're interested in the guide "Applied Differential Equations" by Murray R. Spiegel! applied differential equations murray r spiegel pdf
For mathematics only: $$f(x) = \int_-\infty^\infty f(x) e^-i\omega x dx$$. damped and forced harmonic motion
Hooke's Law, damped and forced harmonic motion, and resonance in structures. Electrical Circuits: Solving LRCcap L cap R cap C applied differential equations murray r spiegel pdf