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Find a unit vector `vecc` if `-hati+hatj-hatk` bisects the angle between vectors `vecc` and `3hati+4hatj`. |
Answer» Let `vecc=xhati+yhatj+zhatk`, where `x^(2)+y^(2)+z^(2)=1`. Unit vector along `3hati+4hatj` is `(3hati+4hatj)/(5)`. The bisector of these two is `-hati+hatj-hatk` (given). Therefore, `" "-hati+hatj-hatk=lamda(xhati+yhatj+zhatk+(3hati+4hatj)/(5))` `" " -hati+hatj-hatk=(1)/(5) lamda [(5x+3)hati+(5y+4)hatj +5zhatk]` `" "(lamda)/(5)(5x+3)=-1, (lamda)/(5)(5y+4)=1, (lamda)/(5)5z=-1` `" "x=-(5+3lamda)/(5lamda), y=(5-4lamda)/(5lamda),z=-(1)/(lamda)` Putting these values in (i), i.e., `x^(2)+y^(2)+z^(2)=1`, we get `" "(5+3lamda)^(2)+(5-4lamda)^(2)+25=25lamda^(2)` `" "25lamda^(2)-10lamda+75=25lamda^(2)` `" "lamda=(15)/(2)` `therefore" "vecc=(1)/(15)(-11hatik+10hatj-2hatk)` |
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