TWO TRIANGLES HAVING THE SAME BASE AND EQUAL AREAS LIE BETWEEN THE SAME PARALLELS. PROVE IT
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∆ABC And ∆ADC Both Lie On The Same Base In A Way That
ar( ∆ABC ) = ar( ∆ABD)
∆ABC And ∆ADB Lie Between The Same Parallel.. ie:- CD || AB
Altitude CE And DF Of ∆ACB & ∆ADB.. On AB .
Now According To Question It's Said That ∆ABC And ∆ABD Both lie On The Same Base ... And Both Have
Equal Area.
Now By Construction We Have ...
CE Perpendicular To AB
And DF Perpendicular To AB
Now We Know That Lines Perpendicular To Same Line Are Parallel To Each Other Therefore ...
CE || DF --- EQ (1)
So Now It's Given That
ar ( ABC ) = ar ( ABD )
Now We Know That ..
Therefore
ar(ABC) = 1/2 × AB × CE
And
ar(ABD) = 1/2 × AB × DF
Now Since Area Of ABC = Area OF ABD
Therefore We Have ...
---- EQ. (2)
Now In Quadrilateral CDEF
CE = DF
And
CE || DF
So We Know That If In A Quadrilateral If One Pair Of Opposite Sides Are Equal And Parallel Then The
Quadrilateral Is Parallelogram.
Therefore
CDEF Is A Parallelogram ...
Therefore
CD || EF ( opposite Sides Of Parallelogram )
That Is ..
ShajuS:
thankyou sir
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