Answer
(a) $\cos{0.8} \approx 0.70$
(b) $\cos{0.8} \approx 0.70$
The values are the same.
Work Step by Step
RECALL:
$\sin{t} = y
\\\cos{t} =x$
(a)
The value of $\color{red}\cos{\color{red}0\color{red}.\color{red}8}$ is equal to the x-coordinate of the red point shown in the attached image below.
Thus, using the given figure, $\color{red}\cos{\color{red}0\color{red}.} \color{red}8\color{red}\approx \color{red}0\color{red}.\color{red}7\color{red}0$.
(b)
Using a calculator in RAD mode gives:
$\cos{0.8} \approx 0.70$
The two values are the same.