how to make a circle using exponential functions

Question

 i am making a project and need help making a circle using exponential functions and another shape using a function with a restricted domain

Answer 1

 

 

 Well the unit circle shall be:

 

 y = f(x) = (1 - x^2)^(1/2) and

y = f(x) = -(1 - x^2)^(1/2)

 

 

The domain restriction is 1-x^2>=0

                                     -x^2>=-1

                                        x^2 <= 1

 

                                     -1 <= x <= 1