write a function a that is 1/ sqrt(1-r^2)^2 +4 * (c^2) *r^2) in matlab

You can write a function in Matlab by following these steps:

1. Open Matlab and create a new function file by selecting "New > Function" from the home tab.
2. Save the function with an appropriate name, such as "function_a".
3. In the function file, define the input arguments using the syntax "function [output] = function_a(r, c)".
4. Write the code for the function using the given formula.
5. The final function file should look like this:

main.m
function [output] = function_a(r, c)
    output = 1/sqrt(1-r^2)^2 + 4 * (c^2) * r^2;
end
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Now you can call this function in your main program or script with the required input arguments to get the output of a.