已知sina=-2根号5/5,且tana

已知sina=-2根号5/5,且tana
已知sina=-2根号5/5,且tana

已知sina=-2根号5/5,且tana
解
sina=-2√5/5
又tana0
∵sin²a+cos²a=1
∴cosa=√1-sin²a
=√1-(-2√5/5)²
=√1-(4/5)
=√5/5
∴tana=sina/cosa
=-2