Another way to do this is to draw a triangle. Since tangent= "opposite leg over near leg", draw a right triangle havine legs of length 3 and 4, with the leg of length 3 opposite angle [itex]\theta[/itex]. Find the length of the hypotenuse using the the Pythagorean theorem (if it isn't obvious) and then it should be simple to find cotan([itex]\theta[/itex]).
Another, rather obvious, way to do this is to use a calculator!