Math, asked by gmishra792, 8 months ago

in an isosceles trapezium ABCD angle A =60 degree and ac=20 cm and ad= 15 cm find the length of a b​

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Answered by Jackie88
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Mensuration

Area of Trapezium

In the adjoining figure, AB...

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Asked on December 26, 2019 by

Mani Lunagaria

In the adjoining figure, ABCD is an isosceles trapezium. If ∠A=60

o

,DC=20 cm and AD=15 cm, find the length of AB.

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ANSWER

In triangle ADM.

cos60

0

=

12

AM

AM=12cos60

0

=6cm

So by symmetry BN=6cm

Hence AB=AM+NM+NB=6+16+6=28cm

Now,

sin60

0

=

12

DM

2

3

=

12

DM

⇒DM=6

3

So are of trapezium =

2

1

×(AB+CD)×DM

=

2

1

(28+16)×6

3

=132

3

cm

2

≈16cm

We get,

length of AB=16cm

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