⇒ Supplementary angles are angles that add up to 180°
⇒ ∠1+∠2=180°(angles on a straight line)
∠2=∠4( Corresponding angles are equal m||n)
⇒*NOTE THE FOLLOWING STATEMENT IS TO MAKE YOU UNDERSTAND,IT MUST NOT BE INCLUDED IN YOUR ANSWERBOOK)
If ∠2=∠4
in the place of ∠2 in the equation ∠1+∠2=180° we can substitute ∠4 since the two angles (∠2 and ∠4) are equal by corresponding angles
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⇒You may include this step now as you now know how ∠4 came up.
∴∠1+(∠4)=180°
∠1+∠4=180°
Now from the above equation we can see that ∠1 and ∠4 are supplementary angles as they both add up to 180°