Question

What does C represent in y=cos(Bx+C)

Answer 1

a constant C?

Answer 2

Well, assuming that B and C are constants, when compared to the original graph of \(y=\cos(x)\), \(y=\cos(Bx+C)=\cos\left[B\left(x+\frac{C}{B}\right)\right]\) will be transformed. Here is the difference:
The transformed function will have a horizontal compression by a factor of B and be shifted to the left, \(\frac{C}{B}\) units.