$)$ Next, use the Pythagorean Theorem $($see Task $5)$ to compute the Cosine for arc

$15$and incorporate this computation into one for the Sine of arc $730$using the

half$-$angle formula; compare also with the value you found in Task $7($c$).$

$($c$)$ Repeat the procedure of part $($b$)$ to determine the Sine of the arc $345,$ then

compare your computation with the value as you found in Task $7($c$).$