Write a complete program that prompts the user for the radius ofasphere, and calculates and prints the volume of that sphere. Use an inline function sphereVolume that returns the result of the following expression: (4.0 / 3.0 * 3.14159 * pow(radius, 3)).

Inline functions are a powerful feature in C++ that optimize the performance of small functions by eliminating the overhead associated with function calls. Rather than jumping to a separate location in memory to execute a function and then returning, an inline function’s code is inserted, or 'inlined', directly into the call site by the compiler.

By marking a function as 'inline', you suggest to the compiler that it should attempt to embed the function directly into the code. This can lead to faster execution, especially for small functions that are called frequently. In the context of calculating the sphere's volume, using an inline function for `sphereVolume` helps in reducing the call overhead since the function is simple and likely to be called multiple times within any given program.

However, it's important to note that 'inline' is merely a request to the compiler. The compiler may ignore this request for inlining if the function is too complex, involves recursion, or has any features that make it unsuitable for inlining, such as static variables. Therefore, inline functions are best used for small, frequently called operations.

The math library in C++ is a powerful toolkit for performing a variety of mathematical operations, which include trigonometric, exponential, logarithmic, and power functions, among others. It is accessed in a C++ program by including the header file `` at the beginning of the program.

For calculating the volume of a sphere, we use the `pow` function from the math library, which raises a number to a specified power. In our case, we use it to cube the radius of the sphere as required by the formula for volume. The `pow` function is a part of the `` library and is often used in mathematical computations that require exponents.

The expression \( 4.0 / 3.0 * 3.14159 * pow(radius, 3) \) leverages the `pow` function to raise the sphere's radius to the third power. Using the math library not only simplifies the process of writing mathematical expressions but also ensures that the calculations are accurate and efficient.

User interaction in C++ is largely handled via the standard input and output streams, provided by the `` library. Standard input (`cin`) and standard output (`cout`) are the primary tools for reading from the keyboard and writing to the screen, respectively.

To obtain the radius of a sphere from the user, `std::cin` is used. It allows the program to wait for user input, store it in a variable, and then use that variable in further calculations. The operator `>>` is used with `std::cin` to direct the input entered by the user into the designated variable.

Subsequently, to display the calculated volume of the sphere, `std::cout` is used along with the `<<` operator, which sends the data to the console. It's crucial for providing feedback to the user and for displaying results, like we do when outputting the calculated volume. Using these tools correctly is essential for creating interactive and user-friendly C++ programs.