Question

7 и 8 задание расписано

Answer 1

S = πr²
P = 2πr
S = 25/π = πr²
r = 5/π
P = 2πr= 2π5/π = 10

sin²α+cos²α=1
$sin alpha = sqrt{1-cos^{2} alpha }$
sin²a = 1 - 4*6/25 = 1/25
sinα = 1/5