CBSE Class XII Maths 2015 Question Papers with Solutions

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Question : 1
Total: 26
If
a
= 2
^
i
+
^
j
+3
^
k
and
b
= 3
^
i
+5
^
j
2
^
k
, then find |
a
×
b
|

Solution:  
Given that
a
= 2
^
i
+
^
j
+3
^
k
and
b
= 3
^
i
+5
^
j
2
^
k

We need to find |
a
×
b
|

a
×
b
= |
^
i
^
j
^
k
213
352
|

=
^
i
(- 2 - 15) -
^
j
(- 4 - 9) +
^
k
(10 - 3)
= - 17
^
i
+ 13
^
j
+ 7
^
k

Hence, |
a
×
b
|
= 172+132+72
|
a
×
b
|
= 507
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