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nickersia Group Title

sinA=-(sprt(3)/2), find two values for cosA without using calculator (x is from 0 do 360 degrees)

  • one year ago
  • one year ago

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  1. rachelfreak123 Group Title
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    can you use the unit circle?

    • one year ago
  2. nickersia Group Title
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    Yes I think you can, (something with leters "CAST" - I don't understand it)... And please write detailed explanation, thanks :)

    • one year ago
  3. rachelfreak123 Group Title
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    • one year ago
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  4. rachelfreak123 Group Title
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    uniti cicle is cool because you just find the value for sin and then the value for cos is with it

    • one year ago
  5. rachelfreak123 Group Title
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    i have no idea what CAST is

    • one year ago
  6. rachelfreak123 Group Title
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    did that help?

    • one year ago
  7. nickersia Group Title
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    Yes it helped for this example, but I still don't know how to the others... For example: If tanA=1/sqrt(3) find 2 values for cosA

    • one year ago
  8. rachelfreak123 Group Title
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    well if it is for other than sin or cos you have to use SOH CAH TOA to find the lenghts of the sides of the triangle all trig crap comes back to triangles....

    • one year ago
  9. nickersia Group Title
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    Yes, and I use TOA so which leads me to tanX=sinX/cosX In this example sinA=1 and cosA=sqrt(3) which is, I think not possible

    • one year ago
  10. rachelfreak123 Group Title
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    well TOA tells you that the opposite side of the triangle is 1 and the ajacent is root 3, so you just need to find the hypot to figure cos

    • one year ago
  11. nickersia Group Title
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    |dw:1358706797888:dw|

    • one year ago
  12. nickersia Group Title
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    If sin is 1 than cos must be 0, that's why I'm confused

    • one year ago
  13. rachelfreak123 Group Title
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    |dw:1358706898345:dw|

    • one year ago
  14. rachelfreak123 Group Title
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    you do not really need the circle part, just a triangle

    • one year ago
  15. rachelfreak123 Group Title
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    the circle would giev you the sign, but atht is uaully just pos and neg

    • one year ago
  16. phi Group Title
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    If sin is 1 than cos must be 0, that's why I'm confused that is true for the unit circle where the radius is 1 but if you are given tan A = \(\frac{1}{\sqrt{3}}\) it is easier to say the leg of the opposite side is 1 and the adjacent side is sqrt(3) and figure out the hypotenuse (radius) using pythagoras

    • one year ago
  17. nickersia Group Title
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    I get the right result +-sprt(3)/2... Thanks, but I'm not sure I understand it clearly yet, I'll try more examples and if I have troubles I'll post :)

    • one year ago
  18. nickersia Group Title
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    Oh yes, radius doesn't have to be 1, you're right :) Thanks phi

    • one year ago
  19. phi Group Title
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    I always do these problems using pythagoras to figure out the missing 3rd side. then soh cah toa to get the trig function they want. you can get 2 different values based on whether x is + or - and y is + or -

    • one year ago
  20. nickersia Group Title
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    |dw:1358707405927:dw| That's how it should look on a circle?

    • one year ago
  21. phi Group Title
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    btw, cast is just a way to remember which quadrant a trig function is positive See http://mathonweb.com/help_ebook/html/cast.htm but I never need it: I just look at the sign of the x and y values

    • one year ago
  22. phi Group Title
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    Yes to your picture notice you will get a positive 1/sqrt(3) if you started with -1/-sqrt(3) (that would give you the other angle or CAST (see link) tells you that tan is + is the 3rd quadrant

    • one year ago
  23. nickersia Group Title
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    Thanks for tips :) Oh, I understand now what it is :D actually you're right, it's not needed, just need to know the coordinates and that sin is on y-axis and cos on x-axis... Thanks a lot, I'm gonna do the rest of the questions :)

    • one year ago
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