As shown in above figure AB and CD are two parallel lines and a line XY passes through them and intersects AB at P & CD at Q. If ∠DQX=x∘ then find ∠APY .
Given ∠DQX=x∘
∵ ∠BPY and ∠DQX are supplementary angles so ∠BPY=180∘−x∘
∠BPY and ∠APY are supplementary angles.
⇒ ∠BPY+∠APY=180∘
⇒ 180∘−x∘+∠APY=180∘ ⇒ ∠APY=x∘
Also, ∠APY=∠DQX=x∘ (Since they are alternate interior angles)