sin(θ-45°)=12/13,135°扫码下载作业帮拍照答疑一拍即得

分类: 作业答案 • 2021-12-18 16:37:36

问题描述：

sin(θ-45°)=12/13,135°

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答

cosa=cos[(a-45)+45]=cos(a-45)cos45-sin(a-45)sin45=[cos(a-45)-sin(a-45)]*(#2/2),#指开根号
90cos(a-45)=-#{1-[sin(a-45)]^2}=-5/13
cosa=（-17/13)*(#2/2)

答

cos(a)=cos((a-45)+45)=cos(a-45)*cos45-sin(a-45)*sin45
135