# Cos(x) question! How would you call 'x'?

1. Sep 10, 2011

### mimzy

So I have this integration to solve but I needed help and I just couldn't make up a term to call that 'x' ><!! the term that is inside the parenthesis!! I know I've learned it somewhere but I just can't remember and it's making me nuts! >A<

Also, what would you do in order to solve an equation that involves lets say sin(x)/cos(2x) [its just made up so I can explain myself a little better :D] and you need to combine both terms... but in order to combine them you gotta make a substitution for that 'x' term ><

thanks in advance :D

2. Sep 10, 2011

### Caramon

Integration by Substitution? Let x = $$\theta$$? The symbol $$\theta$$ is pronounced theta? No idea what you are talking about.

Just so you know, there is no simpler form to:

$$\frac{sin(\theta)}{cos(2 \theta)}$$

IT DOES NOT EQUAL:
$$tan(\frac{1}{2} \theta)$$

No idea if this helps, still have no clue what you are asking...

3. Sep 10, 2011

### mimzy

im just wondering for the name of that theta since it wont always be the same thing on all equations... it changes depending on what u are asked for... like x, theta, pi and so on... just he generic name of that >< sorry if I wasn't clear enough

4. Sep 10, 2011

### Caramon

A variable? There's no set word to describe whatever variable you insert inside of a trigonometric function. You just say that it is the parameter in terms of which the function is defined...?

5. Sep 10, 2011

### Hurkyl

Staff Emeritus
This is a function application expression:
$$A(B)$$
It is composed of two subexpressions:
• The expression $A$, which should be of function type
• The expression $B$, whose type should be contained in domain of $A$
In such expressions, $B$ is sometimes called the "argument", such as in the sentence "$B$ is the argument passed into the function $A$".

6. Sep 10, 2011

### Nowhere Man

Speaking as a programmer, given cos(x), x is the argument or parameter to the function cos(). It can be a literal, such as 20, a variable, or an expression.

Fred