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Malus Law - Cosine squared term?

  1. Mar 6, 2007 #1
    this is just a general trig question:

    We are going over Malus law in physics; the formula is this:
    S = s*cos^2(theta)

    My question is about the cosine squared term in the equation. does this simply mean take the cosine of a number and square it? in other words would this be the same thing as [cos(theta)]^2
     
  2. jcsd
  3. Mar 6, 2007 #2

    arildno

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    Indeed!

    It is an unfortunate notation that confuses a lot of students, but it won't ever go away. you have to live with it.
     
  4. Mar 6, 2007 #3
    I simply tell my students that once upon a time, they wrote it as (sinx)^2, but lazy students kept leaving off the parenthesis and wrote sinx^2, sometimes meaning to take the sine of x, then square that answer; other times meaning to square the x first, then take the sine. To eliminate confusion, when they want the sin value to be squared, they put the squared symbol right next to sin
    [tex]sin^{2}x[/tex]

    So, to shorten [tex](sinx)^2[/tex] write [tex]sin^{2}x[/tex]
    and
    to shorten [tex]sin(x^2)[/tex] write [tex]sinx^2[/tex] (although some people prefer those parenthesis are left in the latter case.)
     
    Last edited: Mar 6, 2007
  5. Mar 6, 2007 #4
    ahhh...thanks for the clarification guys. you've made my day a lot easier!
     
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