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Quick calculator question

  1. Jun 27, 2006 #1
    Hello - I'm sorry if this question doesn't really apply here, but the Math & Science Tutorial wasn't very active so I decided to come here instead...

    What should my calculator mode be in when graphing a hyperbolic WITH trigonometric function? (My function is sinx*coshx - sinhx*cosx). I'm getting 2 different graphs between radian and the degree mode.

    I think it should be in the radian mode...?

    Thanks for your help.
  2. jcsd
  3. Jun 27, 2006 #2
    What kind of calculator are you using?

    I'll assume for a minute that you are using a TI-83/84. When you press the "WINDOW" key (next to "Y=") what is your X min, X max, Y min, Y max values?

    The default is:
    Xmin = -10
    Xmax = 10
    Ymin = -10
    Ymax = 10

    Lets say you are plotting [itex] cos(x) [/itex]
    Well from basic trig you know that:
    [tex] cos(x=\frac{\pi}{2}) = 0 [/tex]
    and that [itex] \frac{\pi}{2}=90 [/itex]
    where [itex] 90 [/itex] is in degrees.

    So if you have your default Xmin, Xmax, ... values above, then this means that you are allowing the calculator to start at the value of [itex] -10 [/itex] and increment up to [itex] 10 [/itex].

    If your calculator is in degree mode you will never see [itex] cox(x) [/itex] hit [itex] 0 [/itex]. Do you see why this is? Our range is too small. But if you put your calculator in radian mode, then guess what... [itex] \frac{\pi}{2}=1.571 [/itex] so we are within our range of values between -10 and 10, thus we will see something useful.

    Also, if we let [itex] y=cos(x) [/itex]. Then, [itex] y [/itex] will range from -1 to 1. So you only need to set
    Ymin = -1
    Ymax = 1
  4. Jun 28, 2006 #3


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    Science Advisor

    Pretty much any math class I have ever taken past high school used radians. I would suggest the same. It really doesn't matter which one you use as long as both functions get the same type of argument, either degrees or radians. Don't mix them.
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