please help me solve this problem

[gitelmana]

i am trying to call some functions in my main function.

[code]#include <iostream>
#include <math.h>

using namespace std;

int a = 1;
double x;
double y;
int c;
double sum;
int z;
int u;
int q;
int w;
int r;
int e;
int der1 = q * e;
int der2 = e - 1;
int der3 = w *r;
int der4 = r - 1;



int multip()
{

	cout << "please chose a number to multiply" << endl;
	cin >> x;
	cout << "the other number too" << endl;
	cin >> y;

	sum = x * y;

	cout << "the result is " << sum << endl;
	return 0;
}





int division()
{
	cout << "please chose a number to divide" << endl;
	cin >> x;
	cout << "pleas decide a number to divide by" << endl;
	cin >> y;

	sum = x / y;

	cout << "the result is " << sum << endl;
	return 0;


}

int sub()
{
	cout << "please chose a number to subtract" << endl;
	cin >> x;
	cout << "pleas decide a number to subtract by" << endl;
	cin >> y;

	sum = x - y;

	cout << "the result is " << sum << endl;
	return 0;
}

int add()
{
	cout << "please chose a number to add" << endl;
	cin >> x;
	cout << "pleas decide a number to add by" << endl;
	cin >> y;

	sum = x + y;

	cout << "the result is " << sum << endl;
	return 0;
}

int root()
{
	cout << "please chose a number to square root" << endl;
	cin >> x;
	sum = sqrt(x);

	cout << "the result is " << sum << endl;
	return 0;
} 

int log()
{
	cout << "please chose a number to log (natural log)" << endl;
	cin >> x;
	sum = log10(x);

	cout << "the result is " << sum << endl;
	return 0;

}

int expo()
{
	cout << "please chose a base" << endl;
	cin >> x;
	cout << "please chose a exponent" << endl;
	cin >> y;

	sum = pow(x, y);

	cout << "the result is " << sum << endl;
	return 0;

}

int main()
{

	while (a <= 1)
	{



		cout << "please chose an operation: for mult. put 1, for dev but 2 for sub put 3, for addition put 4, square root is 5, log is 6, exponents is 7, enter 8 for derivative" << endl;

		cin >> c;

		if (c == 8) {


			cout << "press 1 for product" << endl;
			cin >> u;
			// multiplication		

			if (u == 1)
			{


				// v'
				cout << "for product enter it in the form of ax^n" << endl;
				cout << "first  enter a then enter n" << endl;
				cin >> q;
				cin >> e;


				//u'
				cout << "now enter the second equation in the same format" << endl;
				cin >> w;
				cin >> r;




				cout << "the derivative is: (" << q << "x^" << e << ")" << der3 << "x^" << der4 << "+(" << w << "x^" << r << ")" << der1 << "x^" << der2 << endl;
			}




		}




		if (c == 2)
		{
			int division();
		}

		if (c == 1)
		{
			int multip();
		}

		if (c == 3)
		{
			int sub();
		}

		if (c == 4)
		{
			int add();

			if (c == 5)
			{
				int root();

			}
			if (c == 6)
			{
				int log();

			}

			if (c == 7)
			{
				int expo();

			}

			cout << "Press 1 followed by enter to begin the calculator, or enter 2 to end" << endl;
			cin >> a;
		}


	}
}




	

[salem c]

Please edit your post to put [code][/code] tags around your code (the <> format icon).

[AbstractionAnon]

Two problems:
Lines 73, 78, 83, 88: When you call a function you need ().

Same lines: When you call a function, the compiler must know how to call that function. If the functions definitions are after the call, you need function prototypes:

 int multip();
void division();
void sub();
void add();
void root();

PLEASE ALWAYS USE CODE TAGS (the <> formatting button) when posting code.
It makes it easier to read your code and also easier to respond to your post.
http://www.cplusplus.com/articles/jEywvCM9/
Hint: You can edit your post, highlight your code and press the <> formatting button.