How can I fix my code? I think the issue is the first scanf?

Question

I'm attempting to create a program that computes a value Vt given values for Vo, a, and tm. When I run the code, the program asks the first question then after I give it a value, it speeds through the code without letting me give values for the other two variables. I am programming in C. This is the code:

#include <stdio.h>

main () {

    float Vt;
    float Vo;
    float a;
    float tm;

    printf(" At what time in flight do you wish to know the velocity? To the 
    nearest hundredth. :");
    scanf(" %.2f", &tm);

    printf (" What is the angle of trajectory? :");
    scanf (" %.2f", &a);

    printf (" What is the initial velocity? :");
    scanf (" %.2f", &Vo);

    float sina = sin (a);
    float cosa = cos (a);
    float tana = tan (a);

    Vt = sqrt((pow((Vo * cosa), 2.0)) + (pow((Vo * sina - (9.8 *tm)), 2.0)));

    printf("\n\n\n\n %.3f", Vt);

    return 0;

}

Possible duplicate of https://stackoverflow.com/questions/1669821/scanf-skips-every-other-while-loop-in-c — machine_1, Sep 23 '17 at 04:45
`scanf` doesn't work well for interactive UIs. I'd just use `fgets` (or something similar) to put the data into a string and parse each line individually with `sscanf` (or just `atof`). — mykel, Sep 23 '17 at 04:53

score 3 · Answer 1 · edited Sep 23 '17 at 11:18

3

Your scanf format strings are invalid. Change them to "%f". That is, change

scanf(" %.2f", &tm); to scanf("%f", &tm);
scanf(" %.2f", &a); to scanf("%f", &a);
scanf(" %.2f", &Vo); to scanf("%f", &Vo);

If you intended to scan at most N characters then you must use the "%Nf" format string (such as "%2f" or "%3f"), where N is an integer larger than 0.

edited Sep 23 '17 at 11:18

Basile Starynkevitch

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answered Sep 23 '17 at 11:09

MarkWeston

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How can I fix my code? I think the issue is the first scanf?

1 Answers1