Question

please answer ques. 10

Answer 1

hey !!!!

here is the answer,

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Given: two angles ∠ABC and ∠DEF such that BA is parallel to ED and BC is parallel to EF.

To prove: ∠ABC = ∠DEF or ∠ABC +∠DEF= 180°

Proof: the arms of the angles may be parallel in the same sense or in opp. sense , therefore, three cases arises:

●Case1: when both pairs of arms are parallel in same sense 

( Refer pic )

In this case: BA is parallel to ED and BC is transversal

therefore, ∠ABC= ∠1 [corresponding angles]

again , BC is parallel to EF and DE is transversal

therefore, ∠1= ∠DEF [corresponding angles] 

hence,  ∠ABC= ∠DEF

●Case2: when both pairs of arms are parallel in opp. sense

( Refer pic)

In this case: BA is parallel to ED and BC is transversal

therefore, ∠ABC= ∠1 [corresponding angles]

again , FE is parallel to BC and ED is transversal

therefore, ∠DEF= ∠1 [alternate interior angles] 

hence,  ∠ABC= ∠DEF

●Case3: when one pair of arms are parallel and other pair parallel in opp.

( Refer pic)

 

In this case: BA is parallel to ED and BC is transversal

therefore, ∠EGB= ∠ABC [alternate interior angles]

now, 

BC is parallel to EF  and DE is transversal

therefore, ∠DEF +∠EGB = 180° [co. interior angles] 

⇒∠DEF+∠ABC = 180° [∠EGB=∠ABC]

hence,  ∠ABC and ∠DEF are supplementary.

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Hope it helps u !!!

Cheers ☺☺

# Nikky

Answer 2

I hope helps you
Good luck