sinθ+cosθ=2/3
√2(√2/2cosθ+√2/2sinθ)=2/3
√2cos(θ-π/4）= 2/3
cos(θ-π/4）= √2/3
sin(θ-π/4）= √7/3
tan（θ-π/4）= √7/3/√2/3=√14/2
tan（θ-π/4）= √14/2