Question

State and prove Basic Proportionality Theorem. Using the above theorem, if ABCD is a trapezium whose diagonals intersect each other at O show that AO/OC = BO/OD.​

Answer 1

Answer:

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Step-by-step explanation:

Given: □ABCD is a trapezium where, AB ll CD

Diagonals AC and BD intersect at point O.

Construction: Draw a line EF passing through O and also parallel to AB.

Now, AB ll CD, since by construction, EF ll AB ⇒ EF ll CD

Consider the ΔADC,

EO ll DC

Thus, by Basic proportionality theorem, (AE / ED) = (AO / OC) .... (i)

Now, consider Δ ABD,  

EO ll AB,

Thus, by Basic proportionality theorem, (AE / ED) = (BO / OD) .... (ii)

From (i) and (ii), we have, (AO / OC) = (BO / OD) (since L.H.S of i and ii are equal)

Hence we proved that, (AO / OC) = (BO / OD)