Answer:
Given : ∠ABC is a right angle, ∠D BC is a straight angle.
To prove :∠AB D is a right angle.
Proof: ∠ ABC = 90°[ Given]
∠ D BC= 180° [ D BC is a straight line]
now, ∠ AB D and ∠ AB C are adjacent angles forming linear pair.
∠ AB D +∠ AB C =180° [By linear pair axiom]
⇒∠ AB D + 90= 180°
⇒∠ AB D=180°-90°
⇒∠ AB D=90°
∠AB D is a right angle
Hence proved.
