Question

in the figure L ll M show that ∠1+∠2+∠3=180°.
thanks for answering.

Answer 1

from the figure let BC be extended upto point E
and the line BE must be straight.( 180 degrees)
then angleDEC = angle CBC( if lines are corresponding angles equal )
according to the above assumption angle BCD = angle DCE.
hence DCE is a triangle with angles 1,2,3
we know that angles in a triangle are 180



HENCE PROVED

hope this answer helps u....