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Confusionist

  • one year ago

Can someone help me solve this? cos(x^2+45)+tan(4x+90) = sin(3x+120) A step by step would be great.

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  1. xlegendx
    • one year ago
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    by solving do you mean proving?

  2. Confusionist
    • one year ago
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    Yes. :)

  3. myininaya
    • one year ago
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    What methods have been discussed?

  4. myininaya
    • one year ago
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    We are solving for x not proving this. This isn't an identity.

  5. myininaya
    • one year ago
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    Or does it say to disprove or prove?

  6. Confusionist
    • one year ago
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    Ah yes, my bad. It says solve.

  7. myininaya
    • one year ago
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    Can you tell me what methods in class have been discussed?

  8. Confusionist
    • one year ago
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    None, this is from a book with only problems I picked up at barnes and noble. We haven't done this and wont do it for another year or two. I've had no problems with the book up to this point.

  9. myininaya
    • one year ago
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    can you tell me what methods the book has discussed?

  10. Confusionist
    • one year ago
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    None. It's a book of only problems. It starts from Geometry and works it's way up in problems.

  11. myininaya
    • one year ago
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    Name of book please

  12. Confusionist
    • one year ago
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    Math Review for the High School Classroom

  13. Confusionist
    • one year ago
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    I looked for it online and can't find it.

  14. myininaya
    • one year ago
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    I didn't see the book. :( So there are no examples?

  15. Confusionist
    • one year ago
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    No examples, just questions. :c How did you learn it?

  16. myininaya
    • one year ago
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    Honestly, I don't know without seeing some example or them mentioning some method they want to use.

  17. Confusionist
    • one year ago
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    Ah, okay. Thanks, anyway. :)

  18. shamil98
    • one year ago
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    cos(x^2+45)+tan(4x+90) = sin(3x+120) cos(x^2+45)+sin/cos(4x+90) = sin(3x+120) dividing everything by sin. tan(x^2+45) + sec(4x+90) = 3x + 120 i don't remember trig that well, but you can convert it to this i think.

  19. myininaya
    • one year ago
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    You can't do that... Like you can't divide by the trig part The trig part is a function not a number or variable on its own

  20. shamil98
    • one year ago
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    oh

  21. primeralph
    • one year ago
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    Are the angles in radians or degrees?

  22. primeralph
    • one year ago
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    I'll assume degrees for now.

  23. Confusionist
    • one year ago
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    Degrees, yeah. ^^

  24. hartnn
    • one year ago
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    45,90,120 suggest they are in degrees... we can convert sin and cos in tan, like cos A = tan (sqrt (1-A^2)/A) something like this and then use tan A+tan B formula...... but if thats possible, the algebra is going to be very ugly....

  25. myininaya
    • one year ago
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    but @hartnn tan(90) does not exist you were talking about the sum identity for tan right?

  26. primeralph
    • one year ago
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    @myininaya tan(a+90) = -1/tan(a), since they're perpendicular.

  27. hartnn
    • one year ago
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    not tan(A+B) tan A +tan B , where B = 4x+90 and yeah, tan (A+90) = - cot 90 so maybe convert cos into cot and use cotA-cotB formula... i don't think that will be of any use though....

  28. primeralph
    • one year ago
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    |dw:1388481204906:dw|

  29. myininaya
    • one year ago
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    I don't like the x squared part much.

  30. primeralph
    • one year ago
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    Series solution is what I'd prefer to us,e but not without an attempt with standard algera.

  31. myininaya
    • one year ago
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    or maybe the whole problem i don't see how to do it with algebra/trig He said it was for high school though

  32. hartnn
    • one year ago
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    even wolf doesn't give integral or rational solutions...

  33. Confusionist
    • one year ago
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    Yes, I'm a junior in high school, but the book said High School. It extends way past what I expect to learn in High School, though. I think they may have the age range a bit messed up.

  34. primeralph
    • one year ago
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    No simple way to solve at that level.

  35. myininaya
    • one year ago
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    @primeralph if you want, can you show me your series thing you were talking about? You know if you want to.

  36. Confusionist
    • one year ago
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    I might just go and ask one of the professors at the college I intern at. Thanks for your help, guys. :)

  37. primeralph
    • one year ago
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    First I'd have to convert all to radians.

  38. primeralph
    • one year ago
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    Then find a way to represent the equation as a DE, or simply use the Taylor power series.

  39. myininaya
    • one year ago
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    what is equivalent to a (1 radian) squared? That bugs me. The little square there.

  40. myininaya
    • one year ago
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    What I'm saying is I'm not used to looking at angles being squared

  41. primeralph
    • one year ago
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    |dw:1388481895287:dw|

  42. primeralph
    • one year ago
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    @myininaya Yeah I understand, but you'd have to extend your thinking beyond expecting trig to only apply to angles.

  43. primeralph
    • one year ago
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    It will be extensive, but in the end, there might be real solutions.

  44. myininaya
    • one year ago
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    x^2 and 45 will have different units

  45. myininaya
    • one year ago
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    we have x^2=a^2 (degs)^2 and 45 is just in degs not degs^2

  46. primeralph
    • one year ago
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    The x^2 term will be set to have some correction factor. After taking a look at it, I think it's solvable algebraically. It's just long.

  47. primeralph
    • one year ago
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    And with a lot of restrictions to be imposed.

  48. hartnn
    • one year ago
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    those ugly solutions http://www.wolframalpha.com/input/?i=cos%28x%5E2%2B45%29%2Btan%284x%2B90%29+%3D+sin%283x%2B120%29&dataset=

  49. primeralph
    • one year ago
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    Don't think you used radians. Wolfram is radians by default.

  50. hartnn
    • one year ago
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    doesn't make much difference http://www.wolframalpha.com/input/?i=cos%28x%5E2%2Bpi%2F4%29%2Btan%284x%2Bpi%2F2%29+%3D+sin%283x%2B2pi%2F3%29

  51. myininaya
    • one year ago
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    wolfram doesn't want to solve it this is the way input it cos((x deg)^2+45 deg)+tan(4x deg+90 deg)=sin(3x deg+120 deg) http://www.wolframalpha.com/input/?i=cos%28%28x+deg%29%5E2%2B45+deg%29%2Btan%284x+deg%2B90+deg%29%3Dsin%283x+deg%2B120+deg%29

  52. myininaya
    • one year ago
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    Maybe it doesn't like the unlike units being added either idk

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