sin(x-27°)cos(18°-x)-sin(60°-x)sin(x-18°)
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sin(x-27°)cos(18°-x)-sin(60°-x)sin(x-18°)
为啥答案给的可以化简为sin(x+27°)cos(18°-x)+cos(90°-63°+x)sin(18°-x)
为啥答案给的可以化简为sin(x+27°)cos(18°-x)+cos(90°-63°+x)sin(18°-x)
sin(x-27°)cos(18°-x)-sin(【63°】-x)sin(x-18°)
=sin(x+27°)cos(18°-x)+cos(90°-【63°-x】)sin(18°-x)
=sin(x+27°)cos(18°-x)+cos(90°-63°+x)sin(18°-x)
=sin(x+27°)cos(18°-x)+cos(27°+x)sin(18°-x)
=sin45°
=√2/2
再问: 不好意思追问一下哈 那个sin(x-27°)为啥可以直接划成sin(x+27°)?
再问: 不好意思追问一下哈 那个sin(x-27°)为啥可以直接划成sin(x+27°)?
再答: 没有注意,应该是我抄写错了!
sin(x-27°)cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos(90-(x-27°))cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos(63°-x))cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos【(63°-x)+(x-18°)】
=cos45°
=sin(x+27°)cos(18°-x)+cos(90°-【63°-x】)sin(18°-x)
=sin(x+27°)cos(18°-x)+cos(90°-63°+x)sin(18°-x)
=sin(x+27°)cos(18°-x)+cos(27°+x)sin(18°-x)
=sin45°
=√2/2
再问: 不好意思追问一下哈 那个sin(x-27°)为啥可以直接划成sin(x+27°)?
再问: 不好意思追问一下哈 那个sin(x-27°)为啥可以直接划成sin(x+27°)?
再答: 没有注意,应该是我抄写错了!
sin(x-27°)cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos(90-(x-27°))cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos(63°-x))cos(18°-x)-sin(【63】°-x)sin(x-18°)
=cos【(63°-x)+(x-18°)】
=cos45°
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