5.4 Sum and Difference Trig Formulas


Here are the formulas we have learned:

sin(x+y) = sinx cosy + cosx siny

sin(x-y) = sinx cosy - cosx siny

cos(x+y) = cosx cosy - sinx siny

cos(x-y) = cox cosy + sinx siny

How to derive these formulas:

Now that we know sin(x+y) = cosx siny + sinx cosy

And we know that tanx=sinx/cosx
We can derive tan (x+y)=





















_____________________________________________________________

example problem: