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If |veca|=sqrt(26), |vecb|=7and| veca x...

If `|veca|=sqrt(26), |vecb|=7and| veca xx vecb|=35,` then `veca*vecb =`

A

5

B

7

C

13

D

12

Text Solution

Verified by Experts

The correct Answer is:
B
`|vec(a)xxvec(b)|=35rArr |vec(a)||vec(b)|sin theta = 35 rArr sin theta = (35)/(sqrt(26)xx7)=(5)/(sqrt(26))`
`:. cos theta=sqrt(1-sin^(2)theta)=sqrt(1-(25)/(26))=(1)/(sqrt(26))`.
`:. vec(a).vec(b)=|vec(a)||vec(b)|costheta=sqrt(26)xx7xx(1)/(sqrt(26)) =7`.
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