Khan Academy
Systems of Equations with Elimination (and Manipulation), High School Math
Sal begins this video by "massaging the equations slightly to prepare them for elimination." The equations won't be the only relaxed part of this lesson, which introduces the concept of multiplication to systems of equations. Viewers...
Khan Academy
Proof: sin(a+b)=(cos a)(sin b)+(sin a)(cos b)
Sal proves the sum of angles formula for sine, sin (a+ b) = cos (a) sin (b) + sin (a) cos (b), through a clear but rather non-intuitive proof. The proof is interesting as it uses the SOH-CAH-TOA model and requires one to recall some...
TED-Ed
The Fascinating History of Cemeteries
An irreverently illustrated video history of how human societies have honored their dead is both suitable and thought-provoking for high schoolers in the frame of mind to step back from the sadness of death. Scholars...