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lsugano

  • 3 years ago

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

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

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

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

  4. Mimi_x3
    • 3 years ago
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    then \( 2a = 90\)

  5. lsugano
    • 3 years ago
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    wait how did cot2a= cos2a/sin2a?

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

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

  8. waterineyes
    • 3 years ago
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    *cot

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

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

  11. lsugano
    • 3 years ago
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    im sorry but isnt cot= 1/tana?

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

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

  14. Mimi_x3
    • 3 years ago
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    yes it because what tana?

  15. Mimi_x3
    • 3 years ago
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    what is*

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

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

  18. waterineyes
    • 3 years ago
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    Right..

  19. lsugano
    • 3 years ago
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    ohhhh okay it makes sense

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

  21. Mimi_x3
    • 3 years ago
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    i typed the solution for you already..

  22. waterineyes
    • 3 years ago
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    Multiply by sin(2a) both the sides..

  23. lsugano
    • 3 years ago
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    so it becomes cos2a (sin2a) = 0 (sin2a)

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

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

  26. lsugano
    • 3 years ago
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    so does it become like this?

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  27. waterineyes
    • 3 years ago
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    Yep..

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

  29. waterineyes
    • 3 years ago
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    Welcome dear..

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