sina-cosa=1/5
(sina)^2+(cosa)^2=1
0≤a≤π
sina≥0
解出sina,cosa
sin(2a-π/4)=sin2acosπ/4-cos2asinπ/4
sin2a=2sinacosa
cos2a=1-2(sina)^2
解出来就是答案
(sina=4/5,cosa=3/5,sin2a=24/25,cos2a=-7/25,sin(2a-π/4)=31√2/50)
已知sina-cosa=1/5,0≤a≤π,求sin(2a-π/4)的值
已知sina-cosa=1/5,0≤a≤π,求sin(2a-π/4)的值
数学人气：920 ℃时间：2020-04-01 02:05:45
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