trying to find the squareroot of a number but code doesn't work. C++

Give a shot with this example :

#include <iostream>
#include <cmath>
using std::cout;
using std::cin;

double squareroot(double number){ //function to find squareroot.
    return sqrt(number); //variable for the square of number1
}

int main() { // main function

    int number1 = 0; //first number - integer
    int number2 = 0; //second number - integer
    int number3 = 0; //third number - integer

    cout << "\ntype number1"; //asks user to input first number
    cin >> number1; //stores user input into variable number1

    cout << "\ntype number2"; //asks for second number
    cin >> number2; //stores second number into number2

    cout << "\ntype number3"; // asks for third number
    cin >> number3; //stores third number

    cout << squareroot(number1) << "\n"; //outputs number1
    cout << squareroot(number2) << "\n"; //ouputs number2
    cout << squareroot(number3) << "\n"; //outputs number3

}

You should declare squareroot like:

int squareroot(int number1, int number2, int number3){ //function to find squareroot.
int sQ1 = sqrt(number1); //variable for the square of number1
int sQ2 = sqrt(number2); //variable for the square of number2
int sQ3 = sqrt(number3); //variable for the square of number3
cout << sQ1 << "\n";//outputs the square of number 1
cout << sQ2 << "\n";//outputs the square of number 2
cout << sQ3 << "\n";//outputs the square of number 3
}

and then, call it like:

squareroot(number1, number2, number3);

Anyway, sqrt from math.h accepts a double and returns a double. see http://www.cplusplus.com/reference/cmath/sqrt/

Now this is probably the closest to what I could see that you'd want to do. I'd recommend reading up a bit more on functions and scopes. There isn't much of a single point that you should read up on.

The squareroot() doesn't know about the numbers in main(). You would have to provide them to it. Also, avoid using ints for square roots or other similar functions, ints will truncate (round down) to the nearest integer or even lose data.

#include "stdafx.h"
#include <iostream>
#include <cmath>
using std::cout;
using std::cin;

void squareroot(float n1, float n2, float n3){ //function to find squareroot.
    cout << sqrt(n1) << "\n"; //outputs the square of number 1
    cout << sqrt(n2) << "\n"; //outputs the square of number 2
    cout << sqrt(n3) << "\n"; //outputs the square of number 3
}

int main() { // main function
    float number1 = 0; //first number
    float number2 = 0; //second number
    float number3 = 0; //third number

    cout << "type number1 "; //asks user to input first number
    cin >> number1; //stores user input into variable number1

    cout << "type number2 "; //asks for second number
    cin >> number2; //stores second number into number2

    cout << "type number3 "; // asks for third number
    cin >> number3; //stores third number

    cout << "\n" << number1 << "\n"; //outputs number1
    cout << number2 << "\n"; //ouputs number2
    cout << number3 << "\n"; //outputs number3

    squareroot(number1, number2, number3); //runs function squareroot()
}