In $\triangle ABC$, given that $\angle B = 90^\circ$, and
$ \displaystyle \frac{AB}{AC} = \frac{1}{2} $,
we need to find $\cos C$.
### Step 1: Define Trigonometric Ratio
By definition,
$ \displaystyle \cos C = \frac{\text{adjacent side}}{\text{hypotenuse}} = \frac{AB}{AC} $
### Step 2: Substitute Given Values
Since we are given
$ \displaystyle \frac{AB}{AC} = \frac{1}{2} $,
it follows that:
$ \displaystyle \cos C = \frac{1}{2} $.
### Final Answer:
$ \cos C = \frac{1}{2} $.