Question

过点p(3,-1),向圆M:x^2+y^2-2y-3=0所引切线长

Answer 1

设p与圆心（0,1）距离为d,则切线长^2=d^2-r^2

d=√[3-0)^2+(-1-1)^2]=√13

切线长=√（13-4）=3