How can i use CORDIC ?

What kind of problems exactly? And just a remark:

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use ieee.numeric_std.all;

use ieee.std_logic_signed.all;

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This is a bad idea, mixing numeric_std with one of the non standard std_logic_(un)signed gives weird results and problems. You'd better only include the numeric_std library and use the unsigned/signed types each time you need to do an arithmetic operation.