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Calculator Trig Question

Mai-KeroMai-Kero Registered User regular
edited April 2009 in Help / Advice Forum
So I'm doing some homework for a trig class, and we're supposed to get the exact values of cos(60) and csc(60).

My calculator gives me 5e-1 for the cos, though. What does that even mean? Is this something I'm supposed to do by hand in radians, and if so, how?

Mai-Kero on

Posts

  • VirumVirum Registered User regular
    edited March 2009
    It probably wants you to take the cos in degrees.... look at the unit circle.

    Virum on
  • Little JimLittle Jim __BANNED USERS
    edited March 2009
    Mai-Kero wrote: »
    So I'm doing some homework for a trig class, and we're supposed to get the exact values of cos(60) and csc(60).

    My calculator gives me 5e-1 for the cos, though. What does that even mean? Is this something I'm supposed to do by hand in radians, and if so, how?

    5e-1 = 0.5

    cos(60 degrees) = cos (pi/3) = 1/2 by this circle:

    Unit_Circle_Angles.png

    Little Jim on
    th_crabz.png
  • [Michael][Michael] Registered User regular
    edited April 2009
    The proportions of the sides of a 30-60-90 triangle is something you just gotta memorize (1, 2, sqrt(3)), and to get the values of any trigonometric function you just plug in the sides.

    trig_30_60_90.gif

    SOH CAH TOA is a common thing to have drilled into your head in a trig class (sine=opp/hyp; cosine=adj/hyp; tangent=opp/adj), then you just gotta know that cosecant, secant, and cotangent are just sine, cosine, and tangent flipped around, and you're good to go for finding out trig function values given a triangle.

    cos is adjacent over hypotenuse, so cos(60) is 1 over 2 (1/2). csc is hypotenuse over opposite, so you just plug in the side lengths for that.

    [Michael] on
  • Mai-KeroMai-Kero Registered User regular
    edited April 2009
    Thanks people, you're awesome.

    Mai-Kero on
  • mcdermottmcdermott Registered User regular
    edited April 2009
    5e-1 = 0.5

    For a better explanation, this is called scientific notation. The first number will generally* have the decimal after the first digit (in this case 5.0, so the decimal is omitted, but it could just as easily be 5.237), and the second is the power of 10 you multiply by.

    So 5e-1 = 5*10^(-1) = 0.5

    5e-2 = 5*10^(-2) = 0.05

    5.237e3 = 5.237*10^(3) = 5237

    * - In some applications, you can have up to three digits in front of the decimal and the power will be the nearest power of three, to represent orders of the metric system (kilo, milli, micro, mega, etc.). So 15km would be 15e3 instead of 1.5e4.

    EDIT: I'm guessing you were already familiar with scientific notation in general, but explained it just in case...more likely you just hadn't seen it presented in the E notation before, but were used to actually having "x10^-1" written out.

    mcdermott on
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