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Math Help - Graphs & Degrees

  1. #1
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    Graphs & Degrees

    I'm trying to translate the slope into degrees.

    I know the formula for slope (y2-y1)/(x2-x1) = slope

    The difficultly is now translating that into degrees.

    I saw a formula that suggested it could translate it, but in practice I've found either it doesn't or I'm using it all wrong.

    (slope * 180)/(pi) = degrees

    So as an example of how it's not working; slope is 40/2 = 20.

    (20 * 180)/(pi) = degrees
    (3600)/(3.14) = degrees
    1146 = degrees

    I know I've got something incorrect here, but I don't know what it is.

    Any input is greatly appreciated!
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  2. #2
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    Re: Graphs & Degrees

    Quote Originally Posted by Phoenix999 View Post
    I'm trying to translate the slope into degrees.
    I know the formula for slope (y2-y1)/(x2-x1) = slope
    The difficultly is now translating that into degrees.
    I saw a formula that suggested it could translate it, but in practice I've found either it doesn't or I'm using it all wrong.
    (slope * 180)/(pi) = degrees
    So as an example of how it's not working; slope is 40/2 = 20.
    (20 * 180)/(pi) = degrees
    (3600)/(3.14) = degrees
    1146 = degrees
    I know I've got something incorrect here, but I don't know what it is.
    I am sorry to tell you this, but your posting makes very little sense whatsoever.

    Slope is the tangent of the angle that a line makes with the x-axis in the positive direction.
    So suppose the line has slope m.
    If m\ge 0 then that angle is \theta=\arctan(m)

    If m< 0 then that angle is \theta=\pi+\arctan(m)

    Now in either case a mathematical cave man(i.e. someone who still uses degrees) can use that conversion formula.
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  3. #3
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    Re: Graphs & Degrees

    Thank you for responding. I truly appreciate any help you can give. There is no reason to be sorry. If I knew what I was doing, then I wouldn't be here.

    I have a photo. It is 4000 by 4000 pixels. I use a program (GIMP) to draw a random line x1 y1 to x2 y2. I am able to then ask the program for the specific x & y coordinates. I'm trying to use those coordinates to help adjust the brush's angle to match the line's (for lack of a better word) angle on the photo. I assumed using a slope equation would be the best method.

    I'm hoping you could clarify some items for me.

    First, I do not know what (-) stands for.
    Second, can you translate arctan into caveman
    And lastly, is arctan(m) = arctan * (m)

    If this is the wrong area to make this post, I hope I'm not offending anyone with my simplistic inquiry. I thought this was the basic math area. If it's not, maybe someone can direct me to proper place.

    Thank you and all input is appreciated.
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  4. #4
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    Re: Graphs & Degrees

    Quote Originally Posted by Phoenix999 View Post
    Thank you for responding. I truly appreciate any help you can give. There is no reason to be sorry. If I knew what I was doing, then I wouldn't be here.

    I have a photo. It is 4000 by 4000 pixels. I use a program (GIMP) to draw a random line x1 y1 to x2 y2. I am able to then ask the program for the specific x & y coordinates. I'm trying to use those coordinates to help adjust the brush's angle to match the line's (for lack of a better word) angle on the photo. I assumed using a slope equation would be the best method.

    I'm hoping you could clarify some items for me.

    First, I do not know what (-) stands for.
    Second, can you translate arctan into caveman
    And lastly, is arctan(m) = arctan * (m)

    If this is the wrong area to make this post, I hope I'm not offending anyone with my simplistic inquiry. I thought this was the basic math area. If it's not, maybe someone can direct me to proper place.

    Thank you and all input is appreciated.
    This a mathematics help forum. As such we help people who study mathematics with their questions.
    This is not a forum for those of limited knowledge.
    You need to GOOGLE your question and see what comes up!
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  5. #5
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    Re: Graphs & Degrees

    I am studying mathematics. I just have not reached this level yet. Ironically enough, I am trying to expand my knowledge. I did Google arctan and I assure you It did not produce anything that I could simply relate to your post. Try Googling (-). And the arctan(m), I'm fairly certain it is meant to be multiplied. I was simply asking for a clarification. I was polite in my first post and my second. What happened here is plainly silly.
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  6. #6
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    Re: Graphs & Degrees

    Just as an addition, I've learned that within GIMP Script-fu, I can only use atan within my calculations. How would I convert:

    If m>0 then that angle is (-) = arctan(m)

    If m<0 then that angle is (-) = pi + arctan(m)

    Thanks.
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  7. #7
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    Re: Graphs & Degrees

    The answer to this thread is:

    (180 * Arctan(slope) )/ Pi

    or in Script-fu

    (/ (* 180 (atan slope)) *pi*))

    or more specifically

    (set! slope (/ (- y2 y1)(- x2 x1)))
    (set! angle (/ (* 180 (atan slope)) *pi*))
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