C program to solve Polynomial and Differential Equations

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

float poly(float a[], int, float);
float deriv(float a[], int, float);

int main()
{
    float x, a[10], y1, dy1;
    int deg, i;

    printf("Enter the degree of polynomial equation: ");
    scanf("%d", &deg);

    printf("Ehter the value of x for which the equation is to be evaluated: ");
    scanf("%f", &x);

    for (i = 0; i <= deg; i++) {
        printf("Enter the coefficient of x to the power %d: ", i);
        scanf("%f", &a[i]);
    }

    y1 = poly(a, deg, x);
    dy1 = deriv(a, deg, x);

    printf("The value of polynomial equation for the value of x = %.2f is: %.2f", x, y1);
    printf("\nThe value of the derivative of the polynomial equation at x = %.2f is: %.2f", x, dy1);

    return 0;
}

/* function for finding the value of polynomial at some value of x */

float poly(float a[], int deg, float x)
{
    float p;
    int i;

    p = a[deg];

    for (i = deg; i >= 1; i--) {
        p = (a[i - 1] + x * p);
    }

    return p;
}

/* function for finding the derivative at some value of x */
float deriv(float a[], int deg, float x)
{
    float d[10], pd = 0, ps;
    int i;

    for (i = 0; i <= deg; i++) {
        ps = pow(x, deg - (i + 1));
        d[i] = (deg - i) * a[deg - i] * ps;
        pd = pd + d[i];
    }

    return pd;
}