# Vector problem

## Main Question or Discussion Point

Hi please, someone help me with those problems?

Find the unit vectors u that are prependicular to both i+2j+k and 3i-4j+2k.

the second is:

Find two mutually perpendicular unit vectors that are perpendicular to 2i+3j

Express the vector(s) you seek in terms of unknown coefficients (e.g. ai+bj+ck) and use the definition of 'perpendicular' (i.e. the dotproduct is zero) to find equations you can solve for these unknowns.

TD
Homework Helper
You can also use the fact that the outer product (vectorial) of two vectors gives a new vector which is perpendicular to the first two. Divide by the norm to make it a unit vector.

thanks

OK I gonna try your suggestion

da_willem said:
Express the vector(s) you seek in terms of unknown coefficients (e.g. ai+bj+ck) and use the definition of 'perpendicular' (i.e. the dotproduct is zero) to find equations you can solve for these unknowns.

a vector perpendicular to two seperate vectors is created by using the cross product