
To Prove: \(\frac{BF}{FE}=\frac{BE}{EC}\)
Proof:

In ∆ABC, DE || AC
∴\(\frac{BD}{DA}=\frac{BE}{EC}\) (Basic proportionality theorem)......(i)

In ∆BAE, DF||AE
∴\(\frac{BE}{EC}=\frac{BF}{FE}\) (Basic proportionality theorem)......(ii)
From (i) and (ii), we obtain,
\(\frac{BF}{FE}=\frac{BE}{EC}\)
Hence Proved.
Fill in the blanks using the correct word given in the brackets :
(i) All circles are __________. (congruent, similar)
(ii) All squares are __________. (similar, congruent)
(iii) All __________ triangles are similar. (isosceles, equilateral)
(iv) Two polygons of the same number of sides are similar, if (a) their corresponding angles are __________ and (b) their corresponding sides are __________. (equal, proportional)



| Case No. | Lens | Focal Length | Object Distance |
|---|---|---|---|
| 1 | \(A\) | 50 cm | 25 cm |
| 2 | B | 20 cm | 60 cm |
| 3 | C | 15 cm | 30 cm |