You have already seen a function that has called another function, but you may not have paid close attention to it. In the previous labs, you called a predefined function from the main. You also called the function get_input from the main function in the previous lab. In order to call a function inside another function, you need to have the declaration of the function that is being called before the declaration of the calling function. Here is an example: void that_function(double& x ); double this_function( ); //This function can now call that function int main( ) { double y; .... .... y = this_function( ); .... return 0; } double this_function( ) { double x; .... .... that_function(x ); // that function is being called inside this function return x; } void that_function(double& x ) { .... .... } Exercise 4.4 The following function will use a, b, and c as the coefficients of a quadratic equation to compute b 2 - 4ac. This function calls on another function called get_a_b_c to get the values for a, b, and c. Write the complete program, ex43.cpp, compile and run it.

double bb_4ac( ) { double a, b, c; // Coefficients of a quadratic equation get_a_b_c(a, b, c); return b*b - 4*a*c; }