Solve it in Friday 13th - part 2

Geometry Level 4

cos(2π13)cos(6π13)+cos(2π13)cos(8π13)+cos(6π13)cos(8π13)\cos\left(\dfrac{2\pi}{13}\right)\cos\left(\dfrac{6\pi}{13}\right)+\cos\left(\dfrac{2\pi}{13}\right)\cos\left(\dfrac{8\pi}{13}\right)+\cos\left(\dfrac{6\pi}{13}\right)\cos\left(\dfrac{8\pi}{13}\right)

If the trigonometric expression above can be expressed as αβ-\dfrac{\alpha}{\beta} for coprime positive integers α\alpha and β\beta, find the value of α+β\alpha+\beta.

See Part 1 and Part 3.

×

Problem Loading...

Note Loading...

Set Loading...