Thread: scalar triple product, coplanar vectors.

a = 2i+ 3j +k,
b = i - j,
c = 7i + 3j +2k

must use the scalar triple product to conclude that they are coplanar.

i tried this using a *(b x c)

i also said b was b = i - j +0k ??

so i came out with

2(-2-0) + 3(2-0) + 1(3 - -7)

for -4 +6 + 10

don't think this is correct though, i think they need to be 0.

thanks for any help.

Hello, rcmango!

You dropped a minus-sign . . .

Use the scalar triple product to conclude that they are coplanar.

We have: .

. . . . . . . . .

thanks, ya i'm finding out its really easy to miss signs in these types of problems.