Solve it in Friday 13th - part 3

Geometry Level 5

cos(2π13)cos(6π13)cos(8π13) \large \cos\left(\dfrac{2\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 abc\dfrac{a-\sqrt{b}}{c} for positive integers a,b,ca,b,c with bb is a square-free number and gcd(a,c)=1\text{gcd}(a,c)=1, find a+b+ca+b+c.

See Part 1 and part 2.

×

Problem Loading...

Note Loading...

Set Loading...