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| 1. | Find the angles 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 cmKoi mujhse friendship karega :) | 
| Answer» Explanation: E and F are two points on side PQ and PR in △PQR. (i) PE=3.9 cm, EQ=3 cm and PF=3.6 cm, FR=2.4 cm Using BASIC proportionality theorem, ∴ EQ PE 
 = 3 3.9 
 = 30 39 
 = 10 13 
 =1.3 FR PF 
 = 2.4 3.6 
 = 24 36 
 = 2 3 
 =1.5 EQ PE 
 
  = FR PF 
 
 (II) PE=4 cm, QE=4.5 cm, PF=8 cm, RF=9 cm Using Basic proportionality theorem, ∴ QE PE 
 = 4.5 4 
 = 45 40 
 = 9 8 
 
 RF PF 
 = 9 8 
 
 QE PE 
 = RF PF 
 
 So, EF is parallel to QR. (iii) PQ=1.28 cm, PR=2.56 cm, PE=0.18 cm, PF=0.36 cm Using Basic proportionality theorem, EQ=PQ−PE=1.28−0.18=1.10 cm FR=PR−PF=2.56−0.36=2.20 cm EQ PE 
 = 1.10 0.18 
 = 110 18 
 = 55 9 
 ... (i) FR PE 
 = 2.20 0.36 
 = 220 36 
 = 55 9 
 ... (ii) ∴ EQ PE 
 = FR. PF 
 
 So, EF is parallel to QR. | |