在△ABC中,内角A,B,C的对边分别为a,b,c已知cosA=2分之3,sinB=根号...答:)cosA=2/3,sinA=√5/3,tanA=√5/2 sinB=sin(π-A-C)=sin(A+C)=sinAcosC+cosAsinC=√5/3cosC+2/3sinC 由已知sinB=√5cosC 所以√5cosC=√5/3cosC+2/3sinC 等号两边同时除cosC得 √5=√5/3+2/3tanC tanC=√5 (2)过B作AC垂线,垂足为D tanC=√5,sinC=√5/√6, cosC=1/...
...内角A,B,C的对边分别为a,b,c,已知cosA=2/3,sinB=根号5cosC...答:(1)cosA=2/3,sinA=√5/3,tanA=√5/2 sinB=sin(π-A-C)=sin(A+C)=sinAcosC+cosAsinC=√5/3cosC+2/3sinC 由已知sinB=√5cosC 所以√5cosC=√5/3cosC+2/3sinC 等号两边同时除cosC得 √5=√5/3+2/3tanC tanC=√5 (2)过B作AC垂线,垂足为D tanC=√5,sinC=√5/√6, cosC=...