A cubic formula that you probably haven't seen before!

I just learned this cubic formula with cosine from Wikipedia. The idea is to solve the depressed cubic equation x^3+px+q=0 with the triple angle identity of cosine. However, I don't think this formula is any useful. But is it cool? YES!

How to depress a general cubic polynomial ax^3+bx^2+cx+d    • So you want to prove the cubic formula (fr...  
The cos(3x) identity:    • cos(3x) in terms of cos(x)  
Cubic Equations on Wikipedia: https://en.wikipedia.org/wiki/Cubic_e...

0:00 Solve x^3-28x+48=0
4:36 The proof
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