## 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.

1. xlegendx

by solving do you mean proving?

2. Confusionist

Yes. :)

3. myininaya

What methods have been discussed?

4. myininaya

We are solving for x not proving this. This isn't an identity.

5. myininaya

Or does it say to disprove or prove?

6. Confusionist

Ah yes, my bad. It says solve.

7. myininaya

Can you tell me what methods in class have been discussed?

8. Confusionist

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

can you tell me what methods the book has discussed?

10. Confusionist

None. It's a book of only problems. It starts from Geometry and works it's way up in problems.

11. myininaya

12. Confusionist

Math Review for the High School Classroom

13. Confusionist

I looked for it online and can't find it.

14. myininaya

I didn't see the book. :( So there are no examples?

15. Confusionist

No examples, just questions. :c How did you learn it?

16. myininaya

Honestly, I don't know without seeing some example or them mentioning some method they want to use.

17. Confusionist

Ah, okay. Thanks, anyway. :)

18. shamil98

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

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

oh

21. primeralph

Are the angles in radians or degrees?

22. primeralph

I'll assume degrees for now.

23. Confusionist

Degrees, yeah. ^^

24. hartnn

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

but @hartnn tan(90) does not exist you were talking about the sum identity for tan right?

26. primeralph

@myininaya tan(a+90) = -1/tan(a), since they're perpendicular.

27. hartnn

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

|dw:1388481204906:dw|

29. myininaya

I don't like the x squared part much.

30. primeralph

Series solution is what I'd prefer to us,e but not without an attempt with standard algera.

31. myininaya

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

even wolf doesn't give integral or rational solutions...

33. Confusionist

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

No simple way to solve at that level.

35. myininaya

@primeralph if you want, can you show me your series thing you were talking about? You know if you want to.

36. Confusionist

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

37. primeralph

First I'd have to convert all to radians.

38. primeralph

Then find a way to represent the equation as a DE, or simply use the Taylor power series.

39. myininaya

what is equivalent to a (1 radian) squared? That bugs me. The little square there.

40. myininaya

What I'm saying is I'm not used to looking at angles being squared

41. primeralph

|dw:1388481895287:dw|

42. primeralph

@myininaya Yeah I understand, but you'd have to extend your thinking beyond expecting trig to only apply to angles.

43. primeralph

It will be extensive, but in the end, there might be real solutions.

44. myininaya

x^2 and 45 will have different units

45. myininaya

we have x^2=a^2 (degs)^2 and 45 is just in degs not degs^2

46. primeralph

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

And with a lot of restrictions to be imposed.

48. hartnn
49. primeralph

50. hartnn

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

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

Maybe it doesn't like the unlike units being added either idk