Let P = P={θ :sin θ–cos θ=2cos θ} and {Q=θ:sin θ+cos θ=2sin θ} be two sets, then
P⊂Q and Q~P≠ϕ
Q⊄P
P⊄Q
P =Q
sin θ – cos θ= 2 cos θ
⇔ sinθ = ( 2 +1 ) cos θ
⇔ cosθ = ( 2 -1 ) sin θ
⇔ sin θ + cos θ= 2 sin θ
⇒ P =Q