@banumati234
Prove that the vertically opposite angles of 2 intersecting lines are equal.

Question

@banumati234
Prove that the vertically opposite angles of 2 intersecting lines are equal.

anonymous · Answer

Using what assumptions?

hartnn · Answer

this was @banumati234 's question, she could not post it.
let here come here

hartnn · Answer

ok, you know what are supplementary angles ?

anonymous · Answer

yes.when the sum of 2 angles =180 degree,then the angles are supplementary

hartnn · Answer

good, 
so, 
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i marked 4 angles, can you tell me which angles are supplemenatry ?

anonymous · Answer

angle A,angle B 
angle C,angle D
angle D,angle A
angle B,angle C

anonymous · Answer

to prove that angle A=angle C

hartnn · Answer

oh, excellent! 

so, let angle A = x 
what can you say about angle B ?

anonymous · Answer

180-x

hartnn · Answer

to prove : 

A=C
and B=D

anonymous · Answer

yes..

hartnn · Answer

right, 

since B and C are also supplementary, 
and B= 180-x
what can you say about angle C ?

anonymous · Answer

angle C=x
ok so angle A=angle C=x
thanks!!!!!

hartnn · Answer

correct!
also, since C and D are supplementary, D =180-x
which = B 
so, B=D

anonymous · Answer

thanks again...

hartnn · Answer

welcome ^_^