The discussion about mathematical culture (Cracow 1989)| @romualdd
Trigonometric graphs lesson 6 - Horizontal translation part 1| @magicmonk
Ecuaciones no Lineales y Optimización | 4ta Parte| @abdulmath
Trigonometric graphs lesson 2 - cosine curve, domain, range, period| @magicmonk
Solving Non-homogeneous ODE's: Method of Undetermined Coefficients Part 1| @masterwu