若2sinθ=cosθ,且θ属于(0,π/2) 1.求sinθ-cosθ 2.若sin(θ-ψ)=-√10/10
问题描述：
若2sinθ=cosθ,且θ属于(0,π/2) 1.求sinθ-cosθ 2.若sin(θ-ψ)=-√10/10
答
1,因为(sin^2)θ+(cos^2)θ=1,2sinθ=cosθ,所以(sin^2)θ+4(sin^2)θ=1,则(sin^2)θ=1/5,所以sinθ= 1/√5,cosθ=2/√5,sinθ-cosθ =-1/√5,第二题求啥?2,(sin^2)ψ+(cos^2)ψ=1,sinθcosψ-cosθsinψ=-√10/10 ,...