# Rewrite the trigonometric expression as an algebraic equation

1. Mar 1, 2015

### Tyrion101

What is this asking for? Is it asking for the trig expression in the form of x and y? Or is it asking for something else?

2. Mar 1, 2015

### Staff: Mentor

I don't see how it is possible to write an expression (trig or otherwise) as an equation. They are different kinds of things.

It would help if you told us what the problem is. If it is a homework problem, it needs to be posted in the Homework & Coursework sections (Precalc).

3. Mar 1, 2015

### Tyrion101

When I'm solving trig equations I will simply rewrite them in terms of x and y, so that they are easier to read, then plug back in the trig values when I'm done factoring and otherwise simplifying the problems. Is this a bad habit? I'm just confused as to if this is what it is talking about or if it is something else. Cos(arcos + arcsin) edit I used the wrong term. I meant expression for both, I'm tired and a bit ill.

4. Mar 1, 2015

### Staff: Mentor

No, this is good to do, as long as you are clear about what you are doing when you make the substitution, and then when you undo it. By that, I mean that you write something like "Let B = <whatever>..."
"Cos(arcos + arcsin)" is meaningless, though. arccos of what? arcsin of what? Each of these functions needs an argument; e.g., arccos(y) or arcsin($\pi/2$).

5. Mar 1, 2015

### symbolipoint

You must be clear about what you say both to yourself and to other people. This means you need to use conventional notation. You must have a justifiable reason for assigning sines and cosines to x or y, and not simply do this for convenience of writing steps.

6. Mar 2, 2015

### Tyrion101

Sorry, both arcos and sin have x's, I'm rather tired and sick at the moment. So anything left out just assume it wasn't on purpose.

7. Mar 2, 2015

### symbolipoint

Like I said, your writing needs to be clear both to yourself and to others who read your work. You wrote something which was incomplete, and the readers will often not know what exact interpretation to make.