If vectors ` vec aa n d vec b` are two adjacent sides of a parallelogram, then the vector respresenting the altitude of the parallelogram which is the perpendicular to `a` is ` vec b+( vec bxx vec a)/(| vec a|^2)` b. `( vec a . vec b)/(| vec b|^2)` c. ` vec b-( vec b . vec a)/(| vec a|^2)` d. `( vec axx( vec bxx vec a))/(| vec b|^2)`

If vec a . vec b=betaa n d vec axx vec b= vec c ,t h e n vec b is a. ((beta vec a- vec axx vec c))/(| vec a|^2) b. ((beta vec a+ vec axx vec c))/(| vec a|^2) c. ((beta vec c- vec axx vec c))/(| vec a|^2) d. ((beta vec a+ vec axx vec c))/(| vec a|^2)

Show that ( vec a- vec b)xx( vec a+ vec b)=2( vec axx vec b)dot

Let vec aa n d vec b be two non-zero perpendicular vectors. A vecrtor vec r satisfying the equation vec rxx vec b= vec a can be vec b-( vec axx vec b)/(| vec b|^2) b. 2 vec b-( vec axx vec b)/(| vec b|^2) c. | vec a| vec b-( vec axx vec b)/(| vec b|^2) d. | vec b| vec b-( vec axx vec b)/(| vec b|^2)

If vec axx( vec bxx vec c) is perpendicular to ( vec axx vec b)xx vec c , we may have a. ( vec a . vec c)| vec b|^2=( vec a . vec b)( vec b . vec c) b. vec adot vec b=0 c. vec adot vec c=0 d. vec bdot vec c=0

Find |vec a| and |vec b| if (vec a + vec b).(vec a - vec b) = 3 and 2|vec b| = |vec a| .

If vec a+2 vec b+3 vec c=0,t h e n vec axx vec b+ vec bxx vec c+ vec cxx vec a= 2( vec axx vec b) b. 6( vec bxx vec c) c. 3( vec cxx vec a) d. vec0

If vec a is parallel to vec bxx vec c , then ( vec axx vec b)dot( vec axx vec c) is equal to a. | vec a|^2( vec b . vec c) b. | vec b|^2( vec a . vec c) c. | vec c|^2( vec a . vec b) d. none of these

For any four vectors, prove that ( vec bxx vec c)dot( vec axx vec d)+( vec cxx vec a)dot( vec bxx vec d)+( vec axx vec b)dot( vec cxx vec d)=0.

If vec a , vec ba n d vec c are unit vectors satisfying | vec a- vec b|^2+| vec b- vec c|^2+| vec c- vec a|^2=9, then |2 vec a+5 vec b+5 vec c| is.

If vec a_|_ vec b , then vector vec v in terms of vec aa n d vec b satisfying the equation s vec v . vec a=0a n d vec v . vec b=1a n d[ vec v vec a vec b]=1 is a. vec b/(| vec b|^2)+( vec axx vec b)/(| vec axx vec b|^2) b. vec b/(| vec b|^2)+( vec axx vec b)/(| vec axx vec b|^2) c. vec b/(| vec b|^2)+( vec axx vec b)/(| vec axx vec b|^2) d. none of these