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 ><

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