2條F.4數學問題 高手幫幫忙!!明天要交!!!

Consider OM,ON
OM^2+16=OA^2=r^2
ON^2+9=OC^2=r^2
So OM^2+16=ON^2+9
ON^2-OM^2=7
(ON+OM)(ON-OM)=7
ON-OM=1
So OM^2+16=(OM+1)^2+9
16=2OM+10
OM=3
ON=4
the radius of the circle=5
2
For the first picture, Let B intersect the circle at C
OCA=OAC=(180-70)/2=55
h=90-55=35
k+h+(180-55)=180
h+k=55
k=20
For the second picture
Draw OA and OB
then angle AOB=65*2=130
So x+90+(130/2)=180
and x=25

2008-12-17 18:06:35 補充：
iT SHOULD BE
So x/2+90+(130/2)=180
x=50

好難@@
我F.1 唔識 (我是本ac的弟弟)