How do you evaluate [cos(pi/5) * Cos(2pi/5)][cos(π5)⋅cos(2π5)]?
1 Answer
Apr 18, 2016
This product is equal to 1/4.
Explanation:
See here for a proof:
https://socratic.org/questions/how-do-you-prove-cos36-cos72-1-4#250226
