1. ## help..

Find the vector u=(abc) such that:
(i) u is perpendicular to both the vectors (-1,-1,-2) and (9,-9,0)

(ii) u= $(27)^{1/2}$

(iii) a0

thanks in advance for any help..

2. Originally Posted by omibayne
Find the vector u=(abc) such that:
(i) u is perpendicular to both the vectors (-1,-1,-2) and (9,-9,0)

(ii) u= $(27)^{1/2}$

(iii) a0

thanks in advance for any help..
(i) Take the cross product of (-1, -1, -2) and (9, -9, 0).

(ii) Find the unit in the direction of u and multiply it by $(27)^{1/2}$.

(iii) Multiply u by -1 if it turns out that a < 0 in the above calculations.

3. Originally Posted by mr fantastic
(i) Take the cross product of (-1, -1, -2) and (9, -9, 0).

(ii) Find the unit in the direction of u and multiply it by = $(27)^{1/2}$.

(iii) Multiply u by -1 if it turns out that a < 0 in the above calculations.

ok so i got (-18,-18,18) for the cross product....i still cannot figure out part (ii)...can u explain it a little bit more..i will appreciate that alot..thanks

4. Originally Posted by omibayne
ok so i got (-18,-18,18) for the cross product....i still cannot figure out part (ii)...can u explain it a little bit more..i will appreciate that alot..thanks
Do you know how to find the magnitude of a vector? Do you know how to divide a vector by a scalar. If your answer to both these questions is yes, then you know how to get a unit vector.

5. Originally Posted by mr fantastic
Do you know how to find the magnitude of a vector? Do you know how to divide a vector by a scalar. If your answer to both these questions is yes, then you know how to get a unit vector.
yes i do know and i got the answer..thanks again for ur help