若tanθ=1/3,
则cos²θ+sinθcosθ
=(cos²θ+sinθcosθ)/(sin²θ+cos²θ)
=[(cos²θ/cos²θ)+(sinθcosθ/cos²θ)]/[(sin²θ/cos²θ)+(cos²θ/cos²θ)]
=(1+tanθ)/(tan²θ+1)
=(1+1/3)/(1/9+1)
=6/5