Q11 of 115 Page 8

In Fig. 8.126, which of the following statements must be true?


(i) a + b = d + c


(ii) a + c + e =180°


(iii) b + f = c + e

Let AB, CD and EF intersect at O

∠AOD = ∠COB (Vertically opposite angle)


b = e (i)


∠EOC = ∠DOF (Vertically opposite angle)


f = c (ii)


Adding (i) and (ii), we get


b + f = c + e (iii)


Now,


∠ADE + ∠EOC + ∠COB = 180o


a + f + e = 180o


a + c + e = 180o [From (ii)]

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