# When doing Angular Momentum

#### queenspublic

When doing Angular Momentum, how is it that 2.0(2.12i + 2.12j) x (-3.863i - 1.035j) is equal to 2.0[-2.194k + 8.189k]?

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#### tiny-tim

Science Advisor
Homework Helper
'cos i x j = k and j x i = -k (and ii = jj = 0) #### queenspublic

'cos i x j = k and j x i = -k (and ii = jj = 0) I don't understand.

cos i x j = k ?

So cos 2.12i x 2.12j = -2.194k ?

Please explain it in numbers. How do I get -2.194k + 8.189k ?

#### tiny-tim

Science Advisor
Homework Helper
I don't understand.

cos i x j = k ?

So cos 2.12i x 2.12j = -2.194k ?
he he :rofl:

no, I meant because i x j = k #### queenspublic

he he :rofl:

no, I meant because i x j = k O! I get it! Thanks.

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