TOPICS
Search

Trigonometry Angles--Pi/18

The exact values of cos(pi/18) and sin(pi/18) can be given by infinite nested radicals

sin(pi/(18))=1/2sqrt(2-sqrt(2+sqrt(2+sqrt(2-...)))),

where the sequence of signs +, +, - repeats with period 3, and

cos(pi/(18))=1/6sqrt(3)(sqrt(8-sqrt(8-sqrt(8+sqrt(8-...))))+1),

where the sequence of signs -, -, + repeats with period 3.

See also

Trigonometry Angles, TrigonometryTrigonometry Angles--Pi/9

Explore with Wolfram|Alpha

Cite this as:

Weisstein, Eric W. "Trigonometry Angles--Pi/18." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/TrigonometryAnglesPi18.html

Subject classifications