sin(A) - sin(B) Trig Identity Derivation

[@jan-willemreens9010]

... Good day to you, Very interesting and instructive to see where the SIN(A) - SIN(B) identity comes from, leading to a better understanding (also easier to remember), when applying it, instead of only learning without background information ... worth the time spent for the long run, watching this derivation ... thanks a lot for your math efforts .... best regards, Jan-W