Question 729193
sinθ + 2cosθ = 0
sinθ=-2cosθ
square both sides
sin^2θ=4cos^2θ=4(1-sin^2θ)=4-4sin^2θ
sin^2θ=4-4sin^2θ
5sin^2θ=4
sin^2θ=4/5
take sqrt of both sides
sinθ=2/√5
θ≈2.034 (in quadrant II where sin>0)