Find a unit vector orthogonal to −5 I + 2 J + 10 K and 0 I + 1 J + 0 K:
??? I + ??? J + ??? K

Question

anonymous · Answer

Use cross product.

anonymous · Answer

didnt work

anonymous · Answer

sure it does, [-10, 0, -5] is the answer.

anonymous · Answer

i              j              k
-5           2             10
0             1              0
=-10i+0j-5k which is what YTheManifold stated

anonymous · Answer

i did it but only the 0j is right

anonymous · Answer

check the answer by calculating the scalar product to see if it is orthogonal

anonymous · Answer

what difference does that makes !?

anonymous · Answer

or you could DOT them which will be=0
a*b/||a||||b||=cos(x)
0=cos(x)
cos^-1(0)=x
x=pi/2 or (-3pi/2) which is orthogonal and if the cos^-1(x)=1 or -1 then they are parallel

anonymous · Answer

its not parallel i know that too !

anonymous · Answer

plus i don't need those properties

anonymous · Answer

the unit vector is -10i+0j-5k/sqrt(100+25)
thats a unit vector does that look better?
5sqrt(5)
-2/sqrt(5)i+0j+-1/sqrt(5)k

anonymous · Answer

yeah it does haha thanX

anonymous · Answer

sweet, welcome