麻烦下大家 sinθ+cosθ=7/5,且tanθ>1, 则cos θ= 由于基础不好请过程详细一点!3qsinθ+cosθ=7/5 (sinθ+cosθ)^2 = 49/25 1+ 2sinθcosθ = 49/25 2sinθcosθ = 24/25 1-2sinθcosθ=1/25 (sinθ-cosθ)^2 = 1/25 sinθ-cosθ = 1/5 或 si
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![麻烦下大家 sinθ+cosθ=7/5,且tanθ>1, 则cos θ= 由于基础不好请过程详细一点!3qsinθ+cosθ=7/5 (sinθ+cosθ)^2 = 49/25 1+ 2sinθcosθ = 49/25 2sinθcosθ = 24/25 1-2sinθcosθ=1/25 (sinθ-cosθ)^2 = 1/25 sinθ-cosθ = 1/5 或 si](/uploads/image/z/9306433-1-3.jpg?t=%E9%BA%BB%E7%83%A6%E4%B8%8B%E5%A4%A7%E5%AE%B6+sin%CE%B8%2Bcos%CE%B8%3D7%2F5%2C%E4%B8%94tan%CE%B8%3E1%2C+%E5%88%99cos+%CE%B8%3D+%E7%94%B1%E4%BA%8E%E5%9F%BA%E7%A1%80%E4%B8%8D%E5%A5%BD%E8%AF%B7%E8%BF%87%E7%A8%8B%E8%AF%A6%E7%BB%86%E4%B8%80%E7%82%B9%213qsin%CE%B8%2Bcos%CE%B8%3D7%2F5+%EF%BC%88sin%CE%B8%2Bcos%CE%B8%29%5E2+%3D+49%2F25+1%2B+2sin%CE%B8cos%CE%B8+%3D+49%2F25+2sin%CE%B8cos%CE%B8+%3D+24%2F25+1-2sin%CE%B8cos%CE%B8%3D1%2F25+%EF%BC%88sin%CE%B8-cos%CE%B8%29%5E2+%3D+1%2F25+sin%CE%B8-cos%CE%B8+%3D+1%2F5+%E6%88%96+si)
麻烦下大家 sinθ+cosθ=7/5,且tanθ>1, 则cos θ= 由于基础不好请过程详细一点!3qsinθ+cosθ=7/5 (sinθ+cosθ)^2 = 49/25 1+ 2sinθcosθ = 49/25 2sinθcosθ = 24/25 1-2sinθcosθ=1/25 (sinθ-cosθ)^2 = 1/25 sinθ-cosθ = 1/5 或 si
麻烦下大家 sinθ+cosθ=7/5,且tanθ>1, 则cos θ= 由于基础不好请过程详细一点!3q
sinθ+cosθ=7/5
(sinθ+cosθ)^2 = 49/25
1+ 2sinθcosθ = 49/25
2sinθcosθ = 24/25
1-2sinθcosθ=1/25
(sinθ-cosθ)^2 = 1/25
sinθ-cosθ = 1/5 或 sinθ-cosθ = - 1/5
解得:sinθ = 4/5, cosθ = 3/5
或sinθ = 3/5, cosθ = 4/5 (舍掉,因为tanθ>1)
所以 cosθ = 3/5 其中解得:sinθ = 4/5, cosθ = 3/5
或sinθ = 3/5, cosθ = 4/5 (舍掉,因为tanθ>1)
所以 cosθ = 3/5 这一步不明白怎么算得来的?
麻烦下大家 sinθ+cosθ=7/5,且tanθ>1, 则cos θ= 由于基础不好请过程详细一点!3qsinθ+cosθ=7/5 (sinθ+cosθ)^2 = 49/25 1+ 2sinθcosθ = 49/25 2sinθcosθ = 24/25 1-2sinθcosθ=1/25 (sinθ-cosθ)^2 = 1/25 sinθ-cosθ = 1/5 或 si
sinθ+cosθ=7/5 且sinθ = 4/5
则sinθ-cosθ=7/5-4/5=3/5