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Math4Life Group Title

Find the value of tan (a-b) if cos a = 3/5 , sin = b 5/13, 0° < a < 90°, and 0° < b < 90°

  • one year ago
  • one year ago

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  1. Math4Life Group Title
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    @hartnn think you could help me on this one? :)

    • one year ago
  2. hartnn Group Title
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    know the formula for tan(a-b) ??

    • one year ago
  3. Math4Life Group Title
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    kind of, i'm doing an alternative thing for my teacher where we try to work ahead on stuff we haven't learned yet so I don't really understand the concept, I want the answer because it gives me extra credit, but I want to understand and for you to explain it to me so I know how to do it for the future :)

    • one year ago
  4. Math4Life Group Title
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    @Callisto @campbell_st @completeidiot

    • one year ago
  5. campbell_st Group Title
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    you need to find the missing sides in 2 triangles |dw:1357801664006:dw| find x and y using pythagoras' theorem... this should be easy. then find for angle a.... the ratio for tan(a) and for angle b.... the ratio for tan(b) then substitute the ratios into the expansion of tan(a - b) hope this makes sense

    • one year ago
  6. Math4Life Group Title
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    It kind of makes sense, do you think you could work through the problem with me?

    • one year ago
  7. campbell_st Group Title
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    ok... what are the lengths of x and y...?

    • one year ago
  8. Math4Life Group Title
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    well we haven't figured them out yet

    • one year ago
  9. campbell_st Group Title
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    can you calculate them using pythagoras' theorem \[5^2 = 3^2 + x^2\] and \[13^2 = 5^2 + y^2\]

    • one year ago
  10. Math4Life Group Title
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    x = 4, -4 y = 12, -12

    • one year ago
  11. campbell_st Group Title
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    well with mesurements... you can only use the positives... you can show me -3 metres... but you can show me 3 metres ok... next step what is tan(a) = and tan(b) = both answers will be fractions...

    • one year ago
  12. Math4Life Group Title
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    1.1578 or -1.1578 0.2126 or -0.2126 right?

    • one year ago
  13. campbell_st Group Title
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    nope not as decimals as fractions... just like in the question cos(a) = 3/5 you need to write them like that

    • one year ago
  14. campbell_st Group Title
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    and only use positive values...

    • one year ago
  15. Math4Life Group Title
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    Ok well let me convert them to fractions

    • one year ago
  16. campbell_st Group Title
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    remember tan = opp/adj|dw:1357802645909:dw|

    • one year ago
  17. Math4Life Group Title
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    22/19 and 7/33

    • one year ago
  18. campbell_st Group Title
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    not even close... you said x = 4 and y = 12 so what would tan(a) = and tan (b) =

    • one year ago
  19. campbell_st Group Title
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    |dw:1357802809114:dw|

    • one year ago
  20. Math4Life Group Title
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    a as in x and b as in y, correct?

    • one year ago
  21. campbell_st Group Title
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    use the measurements in the drawing above to write fractions for tan(a) = and tan (b) =

    • one year ago
  22. Math4Life Group Title
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    I am so confused right now, how do i solve for a and b?

    • one year ago
  23. campbell_st Group Title
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    ok... do you understand that tan = opposite/adjacent... ?

    • one year ago
  24. Math4Life Group Title
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    kind of

    • one year ago
  25. campbell_st Group Title
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    ok... from the diagram below |dw:1357803166503:dw| what is tan(a) = just write a fraction using the side measurements given

    • one year ago
  26. Math4Life Group Title
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    4/3

    • one year ago
  27. Math4Life Group Title
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    or 3/5?

    • one year ago
  28. campbell_st Group Title
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    great tan(a) = 4/3 now for angle b |dw:1357803706601:dw| what is tan(b) = as a fraction

    • one year ago
  29. Math4Life Group Title
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    12/13?

    • one year ago
  30. campbell_st Group Title
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    not quite tan = opposite/adjacent so tan(b) = 5/12 ok... do you know the expansion of tan(a - b)....?

    • one year ago
  31. Math4Life Group Title
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    So tan(4/3 - 5/12) which is 30/23

    • one year ago
  32. campbell_st Group Title
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    nope start with the expansion \[\tan(a - b) = \frac{\tan(a) - \tan(b)}{1 + \tan(a)\tan(b)}\] so substitute tan(a) = 4/3 and tan(b) = 5/12 then just calculate it out...

    • one year ago
  33. campbell_st Group Title
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    oops it should read \[\tan(a - b) =\frac{ \tan(a) - \tan(b)}{1 + \tan(a)\times \tan(b)}\]

    • one year ago
  34. Math4Life Group Title
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    tan(4/3 - 5/12) = tan(4/3) - tan(5/12)/1 + tan(4/3) tan(5/12)

    • one year ago
  35. campbell_st Group Title
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    nope... just put the fractions in (4/3 - 5/12)/(1 + 4/3 x 5/12)

    • one year ago
  36. Math4Life Group Title
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    which is 33/35

    • one year ago
  37. Math4Life Group Title
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    is 33/35 my final answer?

    • one year ago
  38. Math4Life Group Title
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    Ok i'm not trying to seem pushy but can we hurry it up here? It's 3am here and I have to get up at 5:30am and this is my last problem on my practice test

    • one year ago
  39. Math4Life Group Title
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    I appreciate all your help and time thank you :)

    • one year ago
  40. campbell_st Group Title
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    good luck... you really need to know trig basics to be able to do this problem.

    • one year ago
  41. Math4Life Group Title
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    If I keep working on this with you how long will it take? because I'm extremely tired

    • one year ago
  42. campbell_st Group Title
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    well your answer is close it should be 33/56

    • one year ago
  43. Math4Life Group Title
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    Thank you for everything tonight

    • one year ago
  44. campbell_st Group Title
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    good luck

    • one year ago
  45. Math4Life Group Title
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    Thank you I appreciate it

    • one year ago
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is replying to Can someone tell me what button the professor is hitting...

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