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lsugano

what is cot2a=0 Thus 2a=90˚....how did this happen?

  • one year ago
  • one year ago

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  1. Mimi_x3
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    \[ cot2a = 0 => \frac{cos2a}{sin2a} = 0 => cos2a = 0 => 2a = cos(0)\]

    • one year ago
  2. Mimi_x3
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    wait i made a typo: \[ 2a = cos^{-1}(0)\]

    • one year ago
  3. Mimi_x3
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    since you know that \(cos^{-1}(0) = 90\)

    • one year ago
  4. Mimi_x3
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    then \( 2a = 90\)

    • one year ago
  5. lsugano
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    wait how did cot2a= cos2a/sin2a?

    • one year ago
  6. waterineyes
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    Firstly you should remember that: \[\cos(90) = 0\]

    • one year ago
  7. Mimi_x3
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    because \[ cota = \frac{cosa}{sina}\]

    • one year ago
  8. waterineyes
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    *cot

    • one year ago
  9. waterineyes
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    \[\large \cot(90^{\circ}) = 0\]

    • one year ago
  10. waterineyes
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    So you can replace 0 with cot(90): \[\cot(2a) = \cot(90)\]

    • one year ago
  11. lsugano
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    im sorry but isnt cot= 1/tana?

    • one year ago
  12. Mimi_x3
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    well you can use that method if you remember whats cot(90)

    • one year ago
  13. waterineyes
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    Now as trigonometric ratio is same: So you can equate the angles: \[2a = 90\]

    • one year ago
  14. Mimi_x3
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    yes it because what tana?

    • one year ago
  15. Mimi_x3
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    what is*

    • one year ago
  16. Mimi_x3
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    yes it is but whats tan(a) then?*

    • one year ago
  17. lsugano
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    oh cot also equals to x/y so cos/sin right??

    • one year ago
  18. waterineyes
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    Right..

    • one year ago
  19. lsugano
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    ohhhh okay it makes sense

    • one year ago
  20. lsugano
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    so i get that cos2a/sin2a = 0 but then what is next?

    • one year ago
  21. Mimi_x3
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    i typed the solution for you already..

    • one year ago
  22. waterineyes
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    Multiply by sin(2a) both the sides..

    • one year ago
  23. lsugano
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    so it becomes cos2a (sin2a) = 0 (sin2a)

    • one year ago
  24. waterineyes
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    No.. There is one sin(2a) in the denominator too..

    • one year ago
  25. waterineyes
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    Can't you cancel sin(2a) with sin(2a) on left hand side ??

    • one year ago
  26. lsugano
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    so does it become like this?

    • one year ago
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  27. waterineyes
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    Yep..

    • one year ago
  28. lsugano
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    oh okay now i get the steps! thank you so much @waterineyes @Mimi_x3

    • one year ago
  29. waterineyes
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    Welcome dear..

    • one year ago
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