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mathnoob1

  • 3 years ago

show cos2x = 1 - tan^2 (x) / 1 +tan^2 (x)

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  1. Nikhil619
    • 3 years ago
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    do u know how to start?

  2. mathnoob1
    • 3 years ago
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    |dw:1359466433151:dw|

  3. mathnoob1
    • 3 years ago
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    |dw:1359466643501:dw|

  4. Nikhil619
    • 3 years ago
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    Umm...dont do that...u'll only get cos2x=1...

  5. Nikhil619
    • 3 years ago
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    what is tanx=?i.e what can tanx be written as?

  6. mathnoob1
    • 3 years ago
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    sinx/cosx?

  7. Nikhil619
    • 3 years ago
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    yeah good..so tan^2x = sin^2 x/cos^2 x ?

  8. mathnoob1
    • 3 years ago
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    ya

  9. Nikhil619
    • 3 years ago
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    so nw substitute...and tell me what u get..

  10. mathnoob1
    • 3 years ago
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    1-(sin(^2)x/cos(^2)x / 1+(sin(^2)x/cos(^2)x ?

  11. Nikhil619
    • 3 years ago
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    take lcm..

  12. Nikhil619
    • 3 years ago
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    Simplify more...

  13. Tushara
    • 3 years ago
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    i hope dis helps

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  14. Nikhil619
    • 3 years ago
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    @mathnoob1 u got it?

  15. mathnoob1
    • 3 years ago
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    do we use tan^2+1=sec^2 and 1+cot^2 =csc^2 for proving?

  16. Nikhil619
    • 3 years ago
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    U can use any Identity for proving but here as far as I know only this will work...

  17. mathnoob1
    • 3 years ago
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    any tips to know which identity fit most?

  18. Nikhil619
    • 3 years ago
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    there aren't any methods or anything..see u have 2 sides of a proof right..one side will be some complicated thing...while the other will probably be sumthin u know the direct equation for like here cos2x=cosx-sinx...this u already know...so try converting the complicated thing in terms of the other side equation....

  19. mathnoob1
    • 3 years ago
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    ok

  20. mathnoob1
    • 3 years ago
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    i got it cos2x/1 = cos2x

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