at which x - value does the cosine function attain a maximum value?\no x = 0\no x = π/2\no x = 1\no x = 3π/2

Explanation:

Step1: Recall cosine - function properties

The general form of the cosine function is $y = \cos(x)$. The range of the cosine function is $[- 1,1]$, and $\cos(x)=1$ is the maximum value.

Step2: Find x - values for maximum

We know that $\cos(x) = 1$ when $x = 2k\pi$, where $k\in\mathbb{Z}$ (the set of integers). When $k = 0$, $x=0$.

Answer:

A. $x = 0$