Question

已知圓M:(x+cosθ)²+(y-sinθ)²＝1,

直線l:y＝kx,下面四個(gè)命題:

A.對(duì)任意實(shí)數(shù)k與θ,直線l和圓M相切;

B.對(duì)任意實(shí)數(shù)k與θ,直線l和圓M有公共點(diǎn);

C.對(duì)任意實(shí)數(shù)θ,必存在實(shí)數(shù)k,使得直線l與和圓M相切;

D.對(duì)任意實(shí)數(shù)k,必存在實(shí)數(shù)θ,使得直線l與和圓M相切

其中真命題的代號(hào)是___________(寫(xiě)出所有真命題的代號(hào)).

Answer 1

思路解析:圓心坐標(biāo)為(-cosθ,sinθ),d＝

=|sin(θ+φ)|≤1.

故選BD.

答案:BD