Question

从点P(m,3)向圆C(x+2)^2+(y+2)^2=1引切线,则切线长的最小值是?

Answer 1

圆心到点P(m,3)的距离d=√[(m+2)^2+(3+2)^2]=√(m^2+4m+29)

切线长=√(d^2-r^2)

=√(m^2+4m+28)

=√[(m+2)^2+24]

当m=-2时切线长的最小值=√24=2√6