中四數學 圓形

1)AM = AB/2 = 12/2 = 6 cm AM² + OM² = AO²
6² + OM² = 10²
OM = 8 cm CM = OC - OM = 10 - 8 = 2 cm 2)ON² + CN² = OC²
ON² + (8/2)² = OC² ... ☆
OC = √(ON² + 16) 另一方面,
(ON + MN)² + AM² = OA²
(ON + 2)² + (6/2)² = OC² , 代入 ☆ :
(ON + 2)² + (6/2)² = ON² + (8/2)²
(ON + 2)² - ON² = 16 - 9
2 (2ON + 2) = 7
ON + 1 = 7/4
ON = 3/4 cm

圖片參考：https://s.yimg.com/lo/api/res/1.2//YXBwaWQ9dHdhbnN3ZXJzO3E9ODU-/https://drive.google.com/viewerng/img?id=ACFrOgBs80Tmu4zPY2TJ8ihkW1GDv95uQlMZm4Q39WMXAIzGE7i3xl6tbyIqhhMixSEhJuPECjGdOKeDyp7OUyFMMaVblBE9WZ-wUa1jPwcYIQ4VYmh2kW_lDQtX8sw=&w=800&page=0