How to always remember the angle sum identities

Remember the angle sum identities for sine and cosine? sin (A+B) and cos(A+B) = something something something something. Create your own angle sum diagram that will actually make sense. Put it on your fridge. Show it to your Mum. Impress your friends. (Can also be used for greeting cards.) If you're following the Calculus Made Easy playlist (free book: https://bit.ly/EasyCalculus), this is a thing that Sylvanus Thompson just assumes you know in Chapter XV, How to Deal with Sines and Cosines. ... https://www.youtube.com/watch?v=cumS-yWkOT8