If cos(x+y)=0 prove sin(x+2y)=-sin x

Something interesting can be said using the first fact. We know that gives us some combination of and we know that gives us so the first fact tells us something that will allow us to reduce the second fact nicely:

Now, expanding the second part gives:

Our original assumptions were true; we were able to use the fact to reduce the second equation to an equality.

Also, I think you mean rather than -

the line of

yes

step-by-step explanation: