In Fig. 6.14,  and AP and BP are bisectors of 
 and 
, respectively. Find 
 and AP and PB are the bisectors of 
 and 
, 
We know that the interior angles on the same side of the transversal are supplementary
So,
 …(i)
AP and BP are the bisectors of  and 
 respectively.
                    …(ii)
                 …(iii)
On adding equations (ii) and (iii) we get 
From equation (i)
In ,
Hence