Answer
$\cos 0.8\approx 0.7$
Work Step by Step
For any real number $s$ represented by a directed arc on the unit circle,
$\sin s=y\quad \cos s=x \quad \displaystyle \tan s=\frac{y}{x} (x\neq 0)$
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The point on the unit circle (see below) representing
$s=0.8$
is highlighted,
as is its x-coordinate, $\cos s$.
Using the given grid,
$\cos 0.8\approx 0.7$