Wtf is wrong with this?

Hey, Plump here. I'm learning c++. And I seem to understand it pretty well, so I made a program that find sqrt's. But when I go to build it in Visual Studio 2010, it says this:
------ Build started: Project: Calculator, Configuration: Release Win32 ------

[code]stdafx.cpp
Calculator.cpp
Calculator.cpp(10): error C2065: 'cout' : undeclared identifier
Calculator.cpp(10): error C2065: 'endl' : undeclared identifier
Calculator.cpp(17): error C2084: function 'int main(void)' already has a body
Calculator.cpp(8) : see previous definition of 'main'
Calculator.cpp(20): error C3861: 'sqrt': identifier not found
Calculator.cpp(21): error C2065: 'cout' : undeclared identifier
Calculator.cpp(21): error C2065: 'endl' : undeclared identifier
------ Build started: Project: Calculator, Configuration: Debug Win32 ------
Calculator.cpp
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (10): error C2065: 'cout' : undeclared identifier
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (10): error C2065: 'endl' : undeclared identifier
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (17): error C2084: function 'int main(void)' already has a body
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (8) : see previous definition of 'main'
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (20): error C3861: 'sqrt': identifier not found
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (21): error C2065: 'cout' : undeclared identifier
c:\users\catherine\documents\visual studio 2010\projects\calculator\calculator\calculator.cpp (21): error C2065: 'endl' : undeclared identifier
========== Build: 0 succeeded, 2 failed, 0 up-to-date, 0 skipped ==========

Whats the problem, as I'm only new to coding idk what the hells happening!