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Math Help - Alright, I don't understand the jump from this point to this point...

  1. #1
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    Alright, I don't understand the jump from this point to this point...

    Alright, I'm trying to find 80 degrees in standard position without a thinga-ma-bobber.

    Here are the steps you're supposed to do:

    A. Draw an angle in standard position.
    B. Convert to radian measure using exact values.
    C. Name the reference angle in both degrees and radians.

    260 degrees.

    I drew it at 260 degrees in Quad III.
    Step B I do not know.
    C. The reference angle is 80 degrees and it's 4pi/9.
    I can see where \frac{4\pi}{9}+ \frac{9\pi}{9} would be \frac{13\pi}{9} but that is not how it says to do it in the book. It would be a subtraction problem instead. The example problem and this one are very close...

    \frac{13\pi}{9} is the answer I need to get.
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  2. #2
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by A Beautiful Mind View Post
    Alright, I'm trying to find 80 degrees in standard position without a thinga-ma-bobber.

    Here are the steps you're supposed to do:

    A. Draw an angle in standard position.
    B. Convert to radian measure using exact values.
    C. Name the reference angle in both degrees and radians.

    260 degrees.

    I drew it at 260 degrees in Quad III.
    Step B I do not know.
    C. The reference angle is 80 degrees and it's 4pi/9.
    I can see where \frac{4\pi}{9}+ \frac{9\pi}{9} would be \frac{13\pi}{9} but that is not how it says to do it in the book. It would be a subtraction problem instead. The example problem and this one are very close...

    \frac{13\pi}{9} is the answer I need to get.
    I'm not sure what is going on here, namely why you would have drawn a 270 degree angle when you were asked to work with an 80 degree angle, but let's assume that you are to complete the given steps with the 270, then

    A) Draw the angle on the unit circle.
    B) Use the formula

    radians=(\theta)\frac{\pi}{180^\circ}

    with \theta=270^\circ.

    C) Find the refrence angle by analyzing the angle that is made between \theta and the x-axis.
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  3. #3
    MHF Contributor

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    Perhaps A Beautiful Mind has edited his post since your response, but I see 260 degrees, not 270. That will give a reference angle of 80 degrees from the negative x axis: 260- 180= 80. [tex]\frac{\pi}{180}(260)= \frac{13\pi}{9} radians. The reference angle in radians is \frac{13\pi}{9}- \pi=\frac{13- 9}{9}\pi= \frac{4}{9}\pi. You could also calculate that as \frac{\pi}{180}(80)=  \frac{4}{9}\pi.
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