Trigonometry or elementary algebra?

Geometry Level 5

\[\large \sqrt[3]{\cos\left( \frac{2\pi}{7} \right)} + \sqrt[3]{\cos \left(\frac{4\pi}{7}\right)} + \sqrt[3]{\cos \left(\frac{8\pi}{7}\right)} \]

If the value of the trigonometric expression above equals to \[ \displaystyle \large \sqrt[3]{\frac{1}{d}( a - b\sqrt[b]{c})} \] where \(a,b,c\) and \(d\) are positive integers, find the value of \(a+b+c+d \).

×

Problem Loading...

Note Loading...

Set Loading...