Diagonals AC and BD of a trapezium ABCD with AB||DC intersect each other at the point O. Using a similarity criterion for two triangles, show that OAOC=OBOD.
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Solution
Given: ABCD is a trapezium with AB∥DC. O is the point of intersection of two diagonals To Prove: OAOC=OBOD Proof: In △AOB and △DOC ∠BAO=∠OCD (Alternate Angles) ∠ABO=∠ODC (Alternate Angles) ∠AOB=∠DOC (Vertically opposite angles) ∴ By AAA criterion of similarity, △AOB∼△DOC ∴OAOC=OBOD (Corresponding Sides of Similar Triangles)