Jawabanmu

2014-03-22T11:14:40+07:00
Tan (-120) = tan (-120-60) = tan -60 =  \sqrt{3}
cos = (-225)= cos (-225+180) = cos -45 =  \frac{1}{2}  \sqrt{2}  
tan (-330) = tan (360-330)=tan 30 =tan -30 =  \frac{1}{3}  \sqrt{3}
maaf kalau salah , semoga membantu ya kak
2014-03-22T11:23:49+07:00
Rumus - rumusnya :

tan (-120) = tan (60 - 180)
=  \frac{tan 60 - tan 180}{1 + tan60.tan180}

cos (-225) = cos (45 - 270)
= cos45 cos270 + sin45 sin270

tan (-330) = tan (30 - 360 )
=  \frac{tan 30 - tan 360}{1 + tan30.tan360}