1.若α∈,则-等于 ( )
A.cos α-sin α B.cos α+sin α
C.-cos α+sin α D.-cos α-sin α
【解析】选B.因为α∈,
所以sin α<0,cos α>0,
则-=-
=|cos α|-|sin α|=cos α-(-sin α)=cos α+sin α.
2.设a=cos 6°-sin 6°,b=,c=,则有 ( )
A.a>b>c B.a
【解析】选C.a=sin 30°cos 6°-cos 30°sin 6°=sin 24°,
b=sin 26°,c=sin 25°,所以a
