imaginary

#include<stdio.h>
double realAns,imgAns;
void scan_img (double* r1,double* i1,double* r2,double* i2){
    printf ("enter number 1 - real part\n");
    scanf("%lf",&r1);
    printf ("enter number 1 - imaginary part\n");
    scanf("%lf",&i1);
    printf ("enter number 2 - real part\n");
    scanf("%lf",&r2);
    printf ("enter number 2 - imaginary part\n");
    scanf("%lf",&i2);
}
void add(double r1, double i1, double r2, double i2){
    realAns = r1+r2;
    imgAns = i1+i2;
}
void subtract(double r1, double i1, double r2, double i2){
    realAns = r1-r2;
    imgAns = i1-i2;
}
void conjugate(double real, double img, double *ansReal, double *ansImg);
void multiply(double real1, double img1, double real2, double img2, double *ansReal,double *ansImg);
void divide(double real1, double img1, double real2, double img2, double *ansReal,double *ansImg);
main(){
    int i=1,op=0;char loopAns;
    double r1,r2,i1,i2;
    do {
        printf("1. Addition\n2. Subtraction\n3. Multiplication\n4. Division\n5. Conjugate\n please enter the operation number\n");
        scanf("%d",&op);
        switch (op){
            case 1:
                scan_img(&r1,&i1,&r2,&i2);
                add(r1,i1,r2,i2);
                printf("(%lf%c%lf) + (%lf%c%lf) = (%lf%c%lf)",r1,(i1<=0)?(i1==0)? ' ':'-':'+',i1,r2,(i2<=0)?(i2==0)? ' ':'-':'+',i2,imgAns,(i1<=0)?(imgAns==0)? ' ':'-':'+',imgAns);
                break;
            case 2:break;
            case 3:break;
            case 4:break;
            case 5:break;
            default : printf("not valid operation\n"); break;
    }
        printf("do you want to run another operation ? \n(yes/no)");
        scanf("%c",&loopAns);
        switch (loopAns){
            case 'y': i=1;break;
            case 'n': i=0;break;
            default : printf("not valid answer . exiting\n");i=0;break;
        }

    }while(i==1);
    return 0;
}