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Confusionist

  • 2 years 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. anonymous
    • 2 years ago
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    by solving do you mean proving?

  2. Confusionist
    • 2 years ago
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    Yes. :)

  3. myininaya
    • 2 years ago
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    What methods have been discussed?

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

  5. myininaya
    • 2 years ago
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    Or does it say to disprove or prove?

  6. Confusionist
    • 2 years ago
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    Ah yes, my bad. It says solve.

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

  8. Confusionist
    • 2 years 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
    • 2 years ago
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    can you tell me what methods the book has discussed?

  10. Confusionist
    • 2 years 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
    • 2 years ago
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    Name of book please

  12. Confusionist
    • 2 years ago
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    Math Review for the High School Classroom

  13. Confusionist
    • 2 years ago
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    I looked for it online and can't find it.

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

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

  16. myininaya
    • 2 years 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
    • 2 years ago
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    Ah, okay. Thanks, anyway. :)

  18. shamil98
    • 2 years 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
    • 2 years 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
    • 2 years ago
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    oh

  21. anonymous
    • 2 years ago
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    Are the angles in radians or degrees?

  22. anonymous
    • 2 years ago
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    I'll assume degrees for now.

  23. Confusionist
    • 2 years ago
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    Degrees, yeah. ^^

  24. hartnn
    • 2 years 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
    • 2 years ago
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    but @hartnn tan(90) does not exist you were talking about the sum identity for tan right?

  26. anonymous
    • 2 years ago
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    @myininaya tan(a+90) = -1/tan(a), since they're perpendicular.

  27. hartnn
    • 2 years 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. anonymous
    • 2 years ago
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    |dw:1388481204906:dw|

  29. myininaya
    • 2 years ago
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    I don't like the x squared part much.

  30. anonymous
    • 2 years 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
    • 2 years 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
    • 2 years ago
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    even wolf doesn't give integral or rational solutions...

  33. Confusionist
    • 2 years 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. anonymous
    • 2 years ago
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    No simple way to solve at that level.

  35. myininaya
    • 2 years 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
    • 2 years 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. anonymous
    • 2 years ago
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    First I'd have to convert all to radians.

  38. anonymous
    • 2 years 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
    • 2 years ago
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    what is equivalent to a (1 radian) squared? That bugs me. The little square there.

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

  41. anonymous
    • 2 years ago
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    |dw:1388481895287:dw|

  42. anonymous
    • 2 years 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. anonymous
    • 2 years ago
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    It will be extensive, but in the end, there might be real solutions.

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

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

  46. anonymous
    • 2 years 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. anonymous
    • 2 years ago
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    And with a lot of restrictions to be imposed.

  48. hartnn
    • 2 years 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. anonymous
    • 2 years ago
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    Don't think you used radians. Wolfram is radians by default.

  50. hartnn
    • 2 years 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
    • 2 years 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
    • 2 years ago
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    Maybe it doesn't like the unlike units being added either idk

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