I am trying to write an algorithm to turn the EV3 robot (https://d2nmr6p48f8xwg.cloudfront.net/content_pictures/pictures/000/001/570/814c51fb41fab7a3e3039ec6a067accc510a9341Lego-Mindstorms-Ev3-Car-Number-1-Robot-Fllcasts.png) towards an object. 
A complete rotation of a wheel corresponds to a rotation of 360 (or -360 if wheels are running backward) degrees. The object is on the left with $- \alpha$ degree to the center. Now I want to rotate the wheels such that the center points to the object so that the robot can move toward the object. In order to turn the robot the left wheels have to rotate backward and the right wheels forward. The question I am asking myself is: To which relativ angle the left and right wheels have to rotate in order to turn toward the object? How could I calculate it? Would it work if I just rotate the left wheels to $-\alpha$ (backward) and the right wheels to $\alpha$ (forward)
While applying the movement of the wheels for the purpose of facing the object, the center of the EV3 robot is stationery. Therefore, the robot wheels will describe arcs of a circle whose center is the center of the robot, and radius equal to $ \sqrt{a^2 + b^2} $ where the separation between the wheels is $2a$ and $2b$. If the radius of the wheels is $R$ then we want
$\sqrt{a^2 + b^2} \alpha = R \phi $
Hence, the angle of rotation of the wheels is
$ \phi = \dfrac{\alpha \sqrt{a^2 + b^2} }{R}$