Points \(A\), \(B\), and \(C\) are located on \(OP\), \(OQ\) and \(OR\). Given that \(AB||PQ\) and \(AC||PR\). Demonstrate that the segment \( BC\) must be parallel to \(QR \). 
YCIND_240214_6037_a_18.png
 
Proof
 
We know that, If a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio.
 
In \(\Delta OPQ\),
 
\(AB ||\)
 
\(\frac{OA}{AP} = \)
- - - - (1)
 
And also in \(\Delta OPR\),
 
\(AC ||\)
 
\(\frac{OC}{CR} = \)
- - - - (2)
 
From (1) and (2),
 
\(\frac{OC}{CR} =\)
 
In \(\Delta OQR\),
 
\(\frac{OC}{CR} = \frac{OB}{BQ}\)
 
By theorem,
 
Thus, \(BC||QR\).
 
Answer variants:
\(PQ\)
\(PR\)
\(\frac{OB}{BQ}\)
\(\frac{OA}{AP}\)