There’s an interesting detail that the article omits, which is that in that long expression, it’s possible to end up with complex numbers under the cube root si

There’s an interesting detail that the article omits, which is that in that long expression, it’s possible to end up with complex numbers under the cube root sign even if the roots of the polynomial are all real! The formula was discovered before mathematicians accepted the idea of imaginary numbers which made the formula suspect in its early history.