Hi. i really need help quick. Im doing a question where I have to find the tangent of a function.

I have 2 vectors r_u and r_v.

$\displaystyle r_u = i + 2uk \ \text{and} \ r_v = j +2vk $

I just need to find the normal vector at the point (1,-1,2) which is given by $\displaystyle r_u * r_v $ but its been so long since ive done this i forgot how to multiply these two.

I have a matrix

i j k

1 0 2u

0 1 2v

after this i have no problem finding the tangent. Please help