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(2010·河南南阳调研)在△ABC中,3sinA+4cosB=6,4sinB+3cosA=1,则C等于( )
A.30° B.150°
C.30°或150° D.60°或120°
.(2010·河南许昌调研)已知sinβ= (<β<π),且sin(α+β)=cosα,则tan(α+β)=( )
A.1 B.2 C.-2 D.
(2010·河南新乡市模拟)设角α终边上一点P(-4a,3a)(a<0),则sinα的值为( )
A. B.-
C. D.-