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प्रश्न
If `|vec"a"|` = 8, `|vec"b"|` = 3 and `|vec"a" xx vec"b"|` = 12, then value of `vec"a" * vec"b"` is ______.
विकल्प
`6sqrt(3)`
`8sqrt(3)`
`12sqrt(3)`
None of these
उत्तर
If `|vec"a"|` = 8, `|vec"b"|` = 3 and `|vec"a" xx vec"b"|` = 12, then value of `vec"a" * vec"b"` is `12sqrt(3)`.
Explanation:
Using the formula `|vec"a" xx vec"b"| = |vec"a"|*|vec"b"| |sintheta|`
We get `theta = +- pi/6`.
Therefore, `vec"a"*vec"b" = |vec"a"|*|vec"b"| costheta`
= `8 xx 3 xx sqrt(3)/2`
= `12sqrt(3)`.
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