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Didáctica y divulgación de la programación

Multiplication sign
Description

Write a program that shows the sign (+, - or 0) of the product of three real numbers, without calculating it.

    Use a sequence of if operators.

Play card
Description

Classical play cards use the following signs to designate the card face: 2, 3, 4, 5, 6, 7, 8, 9, 10, J, Q, K and A. Write a program that enters a string and prints "yes CONTENT_OF_STRING" if it is a valid card sign or "no CONTENT_OF_STRING" otherwise.

Quadratic Equation
Description
Write a program that reads the coefficients a, b and c of a quadratic equation ax2 + bx + c = 0 and solves it (prints its real roots).

We are given an integer number N (read from the console), a bit value v (read from the console as well) (v = 0 or 1) and a position P (read from the console). Write a sequence of operators (a few lines of C# code) that modifies N to hold the value v at the position P from the binary representation of N while preserving all other bits in N. Print the resulting number on the console.

Using bitwise operators, write a program that uses an expression to find the value of the bit at index 3 of an unsigned integer read from the console.

    The bits are counted from right to left, starting from bit 0.
    The result of the expression should be either 1 or 0. Print it on the console.

Write an expression that calculates trapezoid's area by given sides a and b and height h. The three values should be read from the console in the order shown below. All three value will be floating-point numbers.

Write a program that reads the coordinates of a point x and y and using an expression checks if given point (x, y) is inside a circle K({0, 0}, 2) - the center has coordinates (0, 0) and the circle has radius 2. The program should then print "yes DISTANCE" if the point is inside the circle or "no DISTANCE" if the point is outside the circle.

    In place of DISTANCE print the distance from the beginning of the coordinate system - (0, 0) - to the given point.

Write a program that reads an integer N from the console and prints true if the third digit of N is 7, or "false THIRD_DIGIT", where you should print the third digits of N.

    The counting is done from right to left, meaning 123456's third digit is 4.

Write a program that does the following:

    Reads an integer number from the console.
    Stores in a variable if the number can be divided by 7 and 5 without remainder.
    Prints on the console "true NUMBER" if the number is divisible without remainder by 7 and 5. Otherwise prints "false NUMBER". In place of NUMBER print the value of the input number.

Write a program that reads an integer from the console, uses an expression to check if given integer is odd or even, and prints "even NUMBER" or "odd NUMBER", where you should print the input number's value instead of NUMBER.