EXERCISE
1. In Fig. 6.17, (i) and (ii), DE || BC. Find EC in (i) and AD in (ii).
2. E and F are points on the sides PQ and PR respectively of a ∆PQR. For each of the following cases, state whether EF || QR : (i) PE = 3.9 cm, EQ = 3 cm, PF = 3.6 cm and FR = 2.4 cm (ii) PE = 4 cm, QE = 4.5 cm, PF = 8 cm and RF = 9 cm (iii) PQ = 1.28 cm, PR = 2.56 cm, PE = 0.18 cm and PF = 0.36 cm 3. In Fig., if LM || CB and LN || CD, prove that ${AM}/{AB}={AN}/{AD}$ 4. In Fig., DE || AC and DF || AE. Prove that ${BF}/{FE}={BE}/{EC}$ 5. In Fig. DE || OQ and DF || OR. Show that EF || QR. 6. In Fig. 6.21, A, B and C are points on OP, OQ and OR respectively such that AB || PQ and AC || PR. Show that BC || QR. 7. Using Theorem 6.1, prove that a line drawn through the mid-point of one side of a triangle parallel to another side bisects the third side. 8. Using Theorem 6.2, prove that the line joining the mid-points of any two sides of a triangle is parallel to the third side. 9. ABCD is a trapezium in which AB || DC and its diagonals intersect each other at the point O. Show that ${AO}/{BO}={CO}/{DO}$ 10. The diagonals of a quadrilateral ABCD intersect each other at the point O such that ${AO}/{BO}={CO}/{DO}$.Show that ABCD is a trapezium.