1.已知P(1,-5)是a终边上一点,则sin a等于( ) A.1 B.-5 C.-(5/26)根号26 D.根号26
1.已知P(1,-5)是a终边上一点,则sin a等于( ) A.1 B.-5 C.-(5/26)根号26 D.根号26/26
2.角a终边上有一点P(x,5),且cos a=x/13(x≠0),则sin a =
3.已知角a的终边过点(3m-9,m+2),且cos a <0,sin a 大于0,求m的取值范围.
4.已知角a 的终边与单位圆相交于点P(-1/2,y),求sin a,并说明a 是第几象限角.
5.已知角a 的终边在射线y=-3x(x≥0)上,则sin a ·cos a=
A.-(3/10) B.-根号10/10 C.3/10 D.根号10/10