Having problems with functions

I've built a function, which I'm giving three values x, y and a. however when I run it I get the following error:

??? Reference to a cleared variable a.

Error in ==> parallel_inverse at 68
    a = a * pi/180;

This is my function start:

function parallel_inverse(x, y, a)

Does anyone know why I'm getting this error?

[Walter Roberson]

We need to see the code for your routine.

[Ian Phillips]

As in where I call it? Or the code for the whole function? It's just:

>> parallel_inverse(0,0,10);

where I call it. I don't really want to display the whole function as it's coursework and I don't want it plagirised.

[Matt J]

Well, the error message is saying that you cleared the variable "a" somewhere prior to where you try to use it in the line

a = a* pi/180

If you don't want to show your code, then you'll have to go hunting for the clear statement yourself.

[Ian Phillips]

Thanks. I found the problem. first two lines in the function are:

clear;
clc;