In the following figure, if \(x + y = w + z\), then prove that \(AOB\) is a line.
 
YCIND_231205_5809_12.png
 
Proof:
 
We know that , sum of all angles made along  a point is \(^°\)
 
From the given figure, \(∠AOC + ∠BOC + ∠BOD + ∠AOD =\)\(^°\) 
 
\(y + x + w + z =\)\(^°\)
 
From (1), \((x + y) + (x + y) =\)\(^°\)  
 
\(x +\)\(y =\)\(^°\) 
 
\((x + y) =\)\(^°\)
 
\(x + y=\)\(^°\)
 
From this statement it is proved that \(AOB\) is a straight line because the sum of angles made on the line is \(^°\).
 
So, \(AOB\) is a straight line.
 
Hence Proved.