tanθ=2
sinθ/cosθ=2
sinθ=2cosθ
sin²θ+cos²θ=1
5cos²θ=1
cos²θ=1/5
sin²θ+sinθcosθ+2cos²θ
=4cos²θ+2cos²θ+2cos²θ
=8cos²θ
=8/5