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anonymous

  • one year ago

Little confused on this? Just working on parametric equations, I have x= sin theta/2 & y = cos theta/2... and I have to create a plot table between -pie and pie. I don't know if Im supposed to use the radians as the parameter for the plot table or just degrees? i'm confused...

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  1. misty1212
    • one year ago
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    HI!!

  2. misty1212
    • one year ago
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    always use radians, they are numbers

  3. misty1212
    • one year ago
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    if it is \[x=\sin(\frac{\theta}{2}), y=\cos(\frac{\theta}{2})\] you should get a circle

  4. misty1212
    • one year ago
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    actually because of the \(\frac{\theta}{2}\) you get the upper half of a circle

  5. anonymous
    • one year ago
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    right, I see how it's a circle, i'm just a little confused on the radians, because I'm not understanding what values are supposed to correspond on the table?... I'm sorry if this is confusing, because I'm barely refreshing my trig values and stuff, and I'm not understanding just what values do I use as the parameter...

  6. anonymous
    • one year ago
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    so would my value -pie correspond to -1? say for like the first value on my table?... if I was just plugging in the value for sin 0/2?

  7. zepdrix
    • one year ago
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    I guess the start of your interval, \(\rm \theta=-\pi\) would correspond to \(\rm (x,y)=(-1,0)\) yes?

  8. misty1212
    • one year ago
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    here is a nice picture this is what you should get http://www.wolframalpha.com/input/?i=x%3Dsin%28t%2F2%29%2Cy%3Dcos%28t%2F2%29%2C+t+from+-pi+to+pi

  9. anonymous
    • one year ago
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    ok. great. So If i was plotting the points for the table and I started at -pi, and then -3pi/2, -pi/2, etc. up to pi. Would I just plug in the corresponding degree into the function to be able to graph it by hand.. for example, x= sin theta/2 I would plug in for first value sin 1/2 to get my x coordinate?

  10. misty1212
    • one year ago
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    at \(-\pi\) you get \[(\sin(-\frac{\pi}{2}),\cos(-\frac{\pi}{2}))=(0,-1)\]

  11. zepdrix
    • one year ago
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    Ahh woops :) I just assumed sine went with the y coordinate haha

  12. misty1212
    • one year ago
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    yeah it usually does, doesn't it?

  13. zepdrix
    • one year ago
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    Oh maybe I didn't... sin(-pi/2) = -1

  14. zepdrix
    • one year ago
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    Ya I think misty has those backwards :d

  15. anonymous
    • one year ago
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    ok. great. I see what your saying, so If I was to plug in the value for -3pi/2 do I just convert that into degrees and make it sin -3pi/2 /2 ?

  16. misty1212
    • one year ago
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    lol totally backwards

  17. misty1212
    • one year ago
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    i did the cosine first and the sine second, same mistake doe!

  18. zepdrix
    • one year ago
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    degrees? ew ew ew :( \[\large\rm \frac{3\pi/2}{2}=\frac{3\pi}{4}\]

  19. anonymous
    • one year ago
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    oh. ok. I understand now. great. thank you, Yes I was not understanding the x y points. thank you

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