1.

Find the angle between thevectors ` hat i-2 hat j+3 hat ka n d3 hat i-2 hat j+ hat kdot`A. `cos^(-1).(5)/(7)`B. `cos^(-1).(3)/(5)`C. `cos^(-1).(3)/(sqrt(14))`D. none of these

Answer» Correct Answer - A
`cos theta=(vec(a).vec(b))/(|vec(a)||vec(b)|)=([1xx3+(-2)xx(-2)+3xx1])/([sqrt(1^(2)+(-2)^(2)+3^(2))][sqrt(3^(2)+(-2)^(2)+1^(2))])=(10)/(14)=(5)/(7)rArr theta=cos^(-1).(5)/(7)`.


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