# Malus Law - Cosine squared term?

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

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arildno
Homework Helper
Gold Member
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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.

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
$$sin^{2}x$$

So, to shorten $$(sinx)^2$$ write $$sin^{2}x$$
and
to shorten $$sin(x^2)$$ write $$sinx^2$$ (although some people prefer those parenthesis are left in the latter case.)

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ahhh...thanks for the clarification guys. you've made my day a lot easier!