code block -işlem hatası

#include<stdio.h>
#include<stdbool.h>
double resultOfEquation(int n);
bool isPrime(int number);
int entered,m,control_integer = 0;
int a,b,h;
float u;
int k, num;
unsigned long long fact=1LL;
int factorialOfNumber(int num);
char* Weekdays(int numb);
int main()
{
int choice, n, number, a, b, h, u,k,i,m,num,y, numb;
int choice1=1;
while(choice1 ==1)
{
printf("\n chose a number: ");
printf("\n 1. Calculate the result of the equation ");
printf("\n 2. find a number is prime or not ");
printf("\n 3. calculation the area of a trapezium ");
printf("\n 4. calculate the factorial of a number ");
printf("\n 5. Find the weekday ");
printf("\n Enter your choice: ");
scanf("%d", &choice);
switch(choice)
{
case(1):
printf("\n Enter the value of n to find the result of an equation: ");
scanf("%d", &n);
double res = resultOfEquation(n);
printf("\n RESULT OF AN EQUATION IS: %f \n",res);
break;
case(2):
printf("enter a number:");
scanf("%d",&entered);
for (i=2; m< entered ; m++)
{
if (entered % m == 0)
{
printf("the number entered is not prime.");
control_integer = 1;
break;
}
}
if (control_integer == 0)
printf("the number entered is prime.");
break;
case(3):
printf ("please enter the edges:\n");
printf("a edge(lower base):");
scanf("%d",&a);
printf("b edge(upper base):");
scanf("%d",&b);
printf("h(height):");
scanf("%d",&h);
float u;
u=((a+b)*h)/2;
printf("area of a trapezium: %.2f",u);
break;
case(4):
printf("enter any number to calculate factorial:");
scanf("%d",&num);
for (k=1; k<=num; k++)
{
fact=fact*k;
}
printf("factorial of %d = %llu",num,fact);
case(5):
x:
printf("\n Enter a number between (1-7) to find it's week day: ");
scanf("%d", &numb);
if(numb<=0 && numb>7)
{
printf("\n Invalid input. Please enter valid number!!");
goto x;
}
else
{
printf("\n Weekday is: %s",Weekdays(numb));
}
break;
}
printf("\n Do you want to continue again? (1 or 2): ");
int choice1;
scanf("%d", &choice1);
if(choice1==2)
{
break;
}
}
}
double resultOfEquation(int n)
{
int i;
double result1 = 0;
for(i=1;i<=n;i++)
{
result1 = result1 + ((2*2)-3)/(2*2);
}
return result1;
}
bool isPrime(int number)
{
int flag = true;
if (number <= 1)
{
flag = false;
}
else
{
int j;
for (j = 2; j <= number / 2; j++)
{
if ((number % j) == 0)
{
flag = false;
break;
}
}
}
}
double areaOfTrapezium(int lower_base, int upper_base, int height)
{
double area = ((lower_base+upper_base)*height)/2;
return area;
}
int factorialOfNumber(int num)
{
int fact = 1;
int y;
for(y=num;y>=1;y--)
{
fact = fact *y;
}
return fact;
}
char* Weekdays(int numb)
{
if(numb == 1)
{
return "Monday";
}
else if(numb == 2)
{
return "Tuesday";
}
else if(numb == 3)
{
return "Wedenesday";
}
else if(numb == 4)
{
return "Thursday";
}
else if(numb == 5)
{
return "Friday";
}
else if(numb == 6)
{
return "Saturday";
}
else if(numb == 7)
{
return "Sunday";
}
}

^^^^^^^^^^^^^^^^^^^^^^
kod çalışıyor ama çalıştırdığımda 1. işlemi seçtiğimde sonucu yanlış veriyor. hep sıfır çıkıyor sonuç.hatayı bulamadım lütfen yardım edin.