The formula for a cosine graph is: f(x) = acosb(x - k) + h where a is the amplitude, b is the period factor, k is the phase shift and h is the horizontal shift. Knowing that the amplitude is 2, we can already rule out #1 and #2. If the period is 2π, b = 1 because the formula for period is \(\frac{2 \pi }{b}\). The horizontal shift is π, so we plug that in for k, and h = 1. Now, we plug everything in and you get:
f(x) = 2 cos (x - π) + 1
Option 3 is your answer.
Hope this helps!
