发布时间:2021-02-20 14:29:47
已知△ABC中,=,=,·<0,S△ABC=,||=3,| |=5,则与的夹角是( )
A.30° B.-150° C.150° D.30°或150°
C
∵·3·5sinα得sinα=,则α=30°或α=150°.
又∵·<0,∴α=150°.