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

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 ><

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...

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

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...?

Hurkyl
Staff Emeritus
Gold Member
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 $A$".

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