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/*      chap_7_math_example.c   */

/* This example uses two functions --- mytan and main ---       */
/* to calculate the tangent value of a number, and to check     */
/* the calculation using the sin and cos functions.             */

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

/* This function calculates the tangent using the sin and       */ 
/* cos functions.                                               */

double mytan(x)
    double x;
{
    double y,
           y1,
           y2;

    y1 = sin(x);
    y2 = cos(x);

    if (y2 == 0)
        y = 0;
    else
        y = y1 / y2;

    return y;
}
main()
{
    double x;

    /*  Print values: compare   */
    for (x = 0.0; x < 1.5; x += 0.1)
        printf("tan of %4.1f = %6.2f\t%6.2f\n", x, mytan(x), tan(x));
}