Question

геометрическое решение : cos36*cos72

Answer 1

1/2(соs 36 + cos 108)=1/2(cos 36 + sin 18)=1/2((1+sqrt(5)/4) + (-1+sqrt(5))/4)=sqrt(5)/2

Answer 2

Решение:1/2(cos36+cos108)=1|2(cos36sin18)=12((1+sqrt(5)/4)+(-1+sqrt(5)/2