From ∆OAP, we have OP OA ⇒ OP = OA tanα ⇒ OP = R tanα. α tan P A α Let ∠APB = x and ∠APC ... (1) y x–h In DNM, tan DN MN y h N MN DNcot y (x h)cot .
確定！ 回上一頁
