Rewrite the sine fun gion f(x) = 2sin(x+pi/2) -1 as a cosine

To rewrite the function \( f(x) = 2\sin\left(x + \frac{\pi}{2}\right) - 1 \) as a cosine function, we can use the sine to cosine relationship. Recall that:

\[ \sin\left(x + \frac{\pi}{2}\right) = \cos(x) \]

Substituting this into the function, we have:

\[ f(x) = 2\cos(x) - 1 \]

Thus, the rewritten form of the function as a cosine is:

\[ f(x) = 2\cos(x) - 1 \]