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nickersia

  • one year ago

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

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  1. rachelfreak123
    • one year ago
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    can you use the unit circle?

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

  3. rachelfreak123
    • one year ago
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  4. rachelfreak123
    • one year ago
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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

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

  6. rachelfreak123
    • one year ago
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    did that help?

  7. nickersia
    • one year ago
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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

  8. rachelfreak123
    • one year ago
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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....

  9. nickersia
    • one year ago
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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

  10. rachelfreak123
    • one year ago
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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

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

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

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

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

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

  16. phi
    • one year ago
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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

  17. nickersia
    • one year ago
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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 :)

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

  19. phi
    • one year ago
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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 -

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

  21. phi
    • one year ago
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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

  22. phi
    • one year ago
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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

  23. nickersia
    • one year ago
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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 :)

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