In the figure, line \( DE\) is drawn parallel to \( OQ\) and line \( DF\) is drawn parallel to \(OR\). Prove that the segment \(EF\) is parallel to \( QR\).
 
YCIND_240214_6037_a_17.png
 
Proof:
 
In \(\Delta PQO\),
 
\(DE ||\)
 
 
 
 \(\frac{PD}{DO}=\)
- - - - (1)
 
In \(\Delta PRO\),
 
\(DF ||\)
 
By 
 
\(\frac{PD}{DO}=\)
- - - - (2)
 
From (1) and (2),
 
\(\frac{PF}{FR} =\)
 
In \(\Delta PQR\),
 
\(\frac{PF}{FR} =\)
 
By
 
Thus, \(EF||QR\).
Answer variants:
\(\frac{PE}{FR}\)
\(\frac{PE}{EQ}\)
\(OR\)
\(OQ\)
\(\frac{PF}{FR}\)