186.Using Theorem 6.2 (N.C.E.R.T.), prove that the line joining the mid-points of any two sides of a triangle is parallel to the third side.
Given a ∆ABC, in which DE is a line which intersects AB and AC in D and E respectively, such that AD = DB and AE = EC
To Prove : DE || BC Proof: We have.
...(i) Also, AE = EC ...(ii) Comparing (i) and (ii), we get
Therefore, by using converse of Basic proportionality theorem, we have DE || BC.
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Long Answer Type
187.ABCD is a trapezium in which AB || DC and its diagonals intersect each other at the point O. Show that
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188.The diagonals of a quadrilateral ABCD intersect each other at point O such that Show that ABCD is a trapezium.
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189.State which pairs of triangles in the given Fig, are similar. Write the similarity criterion used by you for answering the question and also write the pairs of similar triangles in the symbolic form:
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Short Answer Type
190.
In the given fig. ∆ODC ~ ∆OBA, ∠BOC = 125° and ∠CDO = 70°. Find ∠DOC, ∠DCO and ∠OAB.