## anonymous one year ago Hi. For the cross product problem 1B, how do you get the minus sign for 4k when the 4j X i was positive? (i + 2j) × (2i − 3j) = i × i − 3i × j + 4j × i − 6j × j = 0 − 3k − 4k − 6 · 0

1. IrishBoy123

$$\hat j \times \hat i = - [\hat i \times \hat j ] = - \hat k$$ crossies are not commutative if you look at my avatar, you can see how to remind yourself of this if stuck

2. anonymous

Thanks so much!

3. IrishBoy123

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