CBSE Class 12 Math 2020 Outside Delhi Set 1 Solved Paper

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Question : 21
Total: 36
Section - B

Q. Nos. 21 to 26 carry 2 marks each.
Check if the relation R on the set A={1,2,3,4,5,6} defined as R={(x,y):y is divisible by x} is (i) symmetric (ii) transitive
OR
Prove that:
9π
8
9
4
s
i
n
1(
1
3
)
=
9
4
s
i
n
1(
22
3
)
Given,
A={1,2,3,4,5,6}
R={(x,y):y is divisible by x}
(i) (2,4)R    {4 is divisible by 2 }
But (4,2)∉ R {2 is not divisible by 4}
R is not symmetric.
 

(ii) Let (a,b)R&(b,c)R
b=λa and c=µb
Now, c=µb=µ(λa)(a,c)R
c is divisible by a
R is transitive.
 
OR
L.H.S. =
9π
8
9
4
s
i
n
1
1
3

=
9
4
(
π
2
sin1
1
3
)

=
9
4
(cos1
1
3
)
.
.
.
.
.(1)

Now, let cos1
1
3
=x
.
Then, cosx=
1
3
sinx
=1(
1
3
)
2
=
22
3

x=sin1
22
3
cos1
1
3
=sin1
22
3

L.H.S. =
9
4
s
i
n
1
22
3
= R.H.S.
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