已知sin(0.25pi-x)=5/13,0<x<0.25pi,求cos2x/cos(0.25pi+x)
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解决时间 2021-04-06 12:13
- 提问者网友：练爱
- 2021-04-05 18:40
已知sin(0.25pi-x)=5/13,0<x<0.25pi,求cos2x/cos(0.25pi+x)
最佳答案
- 五星知识达人网友：走死在岁月里
- 2021-04-05 20:19
cos2x/cos(0.25pi+x)
=sin(pi/2-2x)/sin(0.5pi-(0.25pi+x))
=2sin(0.25pi-x)*cos(0.25pi-a)/sin(0.25pi-x)
=2cos(0.25pi-x)
已知sin(0.25pi-x)=5/13,0
就有 24/13
=sin(pi/2-2x)/sin(0.5pi-(0.25pi+x))
=2sin(0.25pi-x)*cos(0.25pi-a)/sin(0.25pi-x)
=2cos(0.25pi-x)
已知sin(0.25pi-x)=5/13,0
就有 24/13
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