Ny-Ålesund 1年以上以前 如圖所示 r^2 = (r - 4)^2 + 8^2 => r = 10 OC = √(10^2 - 2^2) = √96 = 4√6 => CD = 4√6 - (r - 4) = 4√6 - 6 留言