You got your formula a bit garbled.
cos(A-B) = cosAcosB + sinAsinB
Recalling some well-known values, that is
cosθ cosπ + sinθ sinπ
= cosθ(-1) + sinθ(0)
= -cosθ
But then, you know that from working with reference angles in the various quadrants, right?
Use a sum of difference identity to write the expression as a single function theta: cos(theta - pi).
Okay so I know we will use cosAcosA+sinBsinB
I got:
cos(theta)cos(theta)sin(pi)sin(pi)
I don't know how to solve from here and I'm not sure if that is correct.
1 answer
1 answer