If |a−|=2|b−|=5 and |a−×b−|=8, then a−.b−=

Given |a−×b−|=8,|a−|=2,+|b−|=5|a−×b−|2+(a−.b−)2=|a−|2|b−|2⇒64+(a−.b−)2=4(25)⇒(a−.b−)2=36∵a−.b−=6

If |a−|=2|b−|=5 and |a−×b−|=8, then a−.b−=

Given |a−×b−|=8,|a−|=2,+|b−|=5|a−×b−|2+(a−.b−)2=|a−|2|b−|2⇒64+(a−.b−)2=4(25)⇒(a−.b−)2=36∵a−.b−=6

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If $| \bar{a} | = 2 | \bar{b} | = 5$ and $| \bar{a} \times \bar{b} | = 8,$ then $\bar{a} . \bar{b} =$

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Given

$| \bar{a} \times \bar{b} | = 8, | \bar{a} | = 2, + | \bar{b} | = 5$

${| \bar{a} \times \bar{b} |}^{2} + {(\bar{a} . \bar{b})}^{2} = {| \bar{a} |}^{2} {| \bar{b} |}^{2}$

$\Rightarrow 64 + {(\bar{a} . \bar{b})}^{2} = 4 (25)$

$\Rightarrow {(\bar{a} . \bar{b})}^{2} = 36$

$∵ \bar{a} . \bar{b} = 6$

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If $| \bar{a} | = 2 | \bar{b} | = 5$ and $| \bar{a} \times \bar{b} | = 8,$ then $\bar{a} . \bar{b} =$