Maybe you could get a part-time job in the evening.
新人教版高中数学精讲优练课型第三章三角恒等变换3-2简单的三角
恒等变换一课时提升作业必修四-2019最新整理
(25分钟 60分)
一、选择题(每小题5分,共25分)
1.(2015·湖州高一检测)已知cosθ=-,<θ<3π,那么sin等于( )A. B.- C. D.-【解析】选D.因为<θ<3π,所以<<,所以sin<0,
sin=-=-=-.
2.已知tan=3,则cosα=( )
A. B.- C. D.-【解析】选B.cosα=cos2-sin2
====-.
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talk with her4. sleep well5. good for sleepMaybe you could get a part-time job in the evening.
3.=( )
A. B. C.2 D.
【解题指南】70°与20°可以用诱导公式联系起来,10°与20°可以用二倍角公式联系起来.
【解析】选C.因为===2.
4.(2015·宁波高一检测)化简2+的结果是( )A.2sin5 B.4cos5+2sin5 C.-4cos5-2sin5 D.-2sin5 【解析】选D.原式=2+=2|sin5+cos5|+
=2|sin5+cos5|+2|cos5|,
因为<5<,
所以sin5<0,cos5>0且|cos5|<|sin5|, 所以原式=-2(sin5+cos5)+2cos5=-2sin5. 【补偿训练】化简的结果是( )A.-cos 1 B.cos 1 C.cos 1 D.-cos 1【解析】选C.原式=
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talk with her4. sleep well5. good for sleep
新人教版高中数学精讲优练课型第三章三角恒等变换3-2简单的三角恒等变换一课时提升作业必修四-2019最新整理
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