int check_sin(int *sin_array) {
    
    for (int i = 0; i < 9; i++) {
        if (i % 2 != 0) {
            int multiplied = sin_array[i] * 2;
            if (10 <= multiplied && multiplied <= 99) {
                int num1 = multiplied % 10;
                multiplied = multiplied / 10;
                int num2 = multiplied % 10;
                sin_array[i] = num1 + num2;
            }
            else {
                sin_array[i] = multiplied;
            }
        }
    }

    int total;

    for (int i = 0; i < 9; i++) {
        total += sin_array[i];
    }

    if (total % 10 == 0) {
        return 0;
    }

    return 1;
}
Multiply each digit at odd indices of sin_array by 2. If the product is a one-digit number, put it in the corresponding position of the result in sin_array.
If the product is a two-digit number, add the digits together and put the sum in the
corresponding position of the result in sin_array.

Add digits together to get the sum. If sum is divisible by 10, return 0. Otherwise, return 1.