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Homework Help: Multiplying and subtracting coordinates

  1. Feb 4, 2012 #1
    Hello,

    I am hoping someone can help me understand a problem in a text book. It just assumes you know how to do a littel bit of maths, which I don't, and haven't been able to figure out.

    S11 = 0.894 [itex]\angle[/itex] -60.6
    S21 = 3.122 [itex]\angle[/itex] 123.6
    S12 = 0.020 [itex]\angle[/itex] 62.4
    S22 = 0.781 [itex]\angle[/itex] -27.6

    Then, how does |Δ| = |S11 S22 - S12 S21| = |0.696 [itex]\angle[/itex] -83|

    I have tried different things, for example, converting between cartesian and polar etc, but nothing seems to get me there.

    Multiplying the respective r parts, and subtracting as needed seemed to get me close there, but doing the same with the angles didn't work out.

    Thanks.

    -S
     
  2. jcsd
  3. Feb 4, 2012 #2
    Oh, sorry ....I just figured it out!

    Taking a break and coming back to it does help.

    ....just a thought, should I explain how it is done in case anyone else is looking to know this sort of thing?

    I don't know what the protocol would be on that.

    Slán
    -S
     
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