Who knows how the formula of Sin(A+B)=SinACosB+CosASinB in Senior High School Mathematics Compulsory 4 came from?
Hello, to put it simply, we first get the formula of cos(A+B) by multiplying vectors, and then we get the formula of cos(A-B) by summing up the formula SIN (a+b) = COS [π/2-(a+b)] = COS [(π/2-a)-b], and combine the above.