(i) Diagonal BD meets EF at M. By Theorem 7, M and F bisect BD and BC. Adding segment lengths gives EF = (AB + CD)/2. (ii) Both methods work; using parallel line uniqueness is simpler.
Class 9 Ganita Manjari Part 2 chapter 12 question answer
Class 9 Ganita Manjari Part 2 chapter 12 Quadrilaterals solutions
(i) Draw diagonal BD meeting line EF at M. In triangle DAB, line EM through midpoint E parallel to AB bisects BD at M. In triangle BDC, MF ∥ DC bisects BC at F, yielding EF = EM + MF = AB/2 + CD/2 = (AB + CD)/2. (ii) Midpoints of AD and BC join to form EF. Using the uniqueness of a parallel line through E combined with part (i) is simpler than collinearity proofs.
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