Accumulation of a float constant of sqrt(), the function itself, and its direct multiplication

#include <stdio.h>
#include <math.h>

int main()
{
    float init = 7 * 30;
    float x = init, dx = 30 * sqrt(2);
    float y = init;
    float z = init;
    int i;

    printf("init=%.10f\n", init);
    printf("x=%.10f\n", x);
    printf("dx=30*sqrt(2)=%.10f\n", dx);
    printf("y=%.10f\n", y);
    printf("z=%.10f\n", z);
    printf("\n");
    printf("%2s %14s %14s %19s %13s %13s\n", "i", "x+=dx", "y+=30*sqrt(2)",
           "z=init+i*30*sqrt(2)", "x-y", "x-z");
    for (i = 1; i <= 10; i++) {
        x += dx;
        y += 30 * sqrt(2);
        z = init + i * 30 * sqrt(2);
        printf("%2d %14.10f %14.10f %14.10f      %13.10f %13.10f\n", i, x, y,
               z, x - y, x - z);
    }
}

$ cc -o fperror_float fperror_float.c -Wall
$ ./fperror_float
init=210.0000000000
x=210.0000000000
dx=30*sqrt(2)=42.4264068604
y=210.0000000000
z=210.0000000000

 i          x+=dx  y+=30*sqrt(2) z=init+i*30*sqrt(2)           x-y           x-z
 1 252.4264068604 252.4264068604 252.4264068604       0.0000000000  0.0000000000
 2 294.8528137207 294.8528137207 294.8528137207       0.0000000000  0.0000000000
 3 337.2792358398 337.2792358398 337.2792358398       0.0000000000  0.0000000000
 4 379.7056274414 379.7056579590 379.7056274414      -0.0000305176  0.0000000000
 5 422.1320190430 422.1320800781 422.1320495605      -0.0000610352 -0.0000305176
 6 464.5584106445 464.5585021973 464.5584411621      -0.0000915527 -0.0000305176
 7 506.9848022461 506.9849243164 506.9848632812      -0.0001220703 -0.0000610352
 8 549.4111938477 549.4113159180 549.4112548828      -0.0001220703 -0.0000610352
 9 591.8375854492 591.8377075195 591.8376464844      -0.0001220703 -0.0000610352
10 634.2639770508 634.2640991211 634.2640991211      -0.0001220703 -0.0001220703