過P(5,-3),傾斜角為a,且cosa=-3/5的直線交圓x方+y方=1於P1,P2兩點,求PP1*PP2和P1P2弦中點座標(用參數方 P1P*PP2=t1t2=330

過P(5,-3),傾斜角為a,且cosa=-3/5的直線交圓x方+y方=1於P1,P2兩點,求PP1*PP2和P1P2弦中點座標(用參數方 P1P*PP2=t1t2=330

COS=0.6,所以sin=.8
設直線L x=5-0.6T
y=-3+0.8T
代入圓得0.1t^2+10.8t+33=0
P1P*PP2=t1t2=330
中點wei(-116/25,-87/25)