In the above figure, in ∆ABC, BC is extended to E such that CE= BC. IF D is the mid point of AC and ED cuts AB at F, Find the value of
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Construction: Through D, draw a line parallel to AB cutting AE at G and BE at H. Now, through C, draw a line parallel to BA cutting AE at I and ED at J.
Solution:
In ∆EFB
FD= 2 1 ED. (Basic Proportionality Theorem)
In ∆CAB
CH=BH= 2 1 BC (Mid-Point Theorem)
=> HC=EC
In ∆EDH
EJ=DJ= 2 1 ED. (Mid-Point Theorem)
=> DJ=DF
=> ∆AFD is congruent to ∆CJD
=> AF=JC=a
In ∆AEF
IJ= 3 1 AF. (Basic Proportionality Theorem)
c= 3 1 a
In ∆AEB
CI= 3 1 BA= 3 b . (Basic Proportionality Theorem)
3 b =c+a (CI=a+c)
3 b = 3 a +a
a= 4 b
a b =4