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Kweku

  • 2 years ago

write 3(cos225 +isin225) in the form a + ib.

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  1. ZeHanz
    • 2 years ago
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    225 degrees rings a bell, no?

  2. Kweku
    • 2 years ago
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    it is complex numbers

  3. ZeHanz
    • 2 years ago
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    Not yet ;) I meant that sin225 and cos225 are supposed to be well-known numbers: they have to do with the 45-45-90 degree triangle, with sides a, a and a√2. Does that ring a bell? See image. Both sin225 and cos225 are: \[-\frac{ 1 }{ 2 }\sqrt{2}\]

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  4. Kweku
    • 2 years ago
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    you mean right angled triangle?

  5. ZeHanz
    • 2 years ago
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    yeah

  6. Kweku
    • 2 years ago
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    so you mean the angles should be in the first quadrant?

  7. ZeHanz
    • 2 years ago
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    No, 225 is in the third quadrant. I only meant that in the 3rd quadrant you get the same values (just negative) as in the triangle with 45-45-90 degrees.

  8. ZeHanz
    • 2 years ago
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    Therefore you now have \[3(-\frac{ 1 }{ 2 }\sqrt2+i \cdot -\frac{ 1 }{ 2 }\sqrt 2)\]And if you work out the brackets you're done.

  9. Kweku
    • 2 years ago
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    Yeah I get you but that does not make any change.

  10. ZeHanz
    • 2 years ago
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    Is your problem solved then?

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