Trig Help Plz!!!

[Lestat]

I need some help FAST!!!!!!!!!
can anyone prove this relation???
cos (pi/5) + cos (2pi/5) = 0.25
you can prove it in degrees if you want to:
cos 36 + cos 72 = 0.25
Thanks

 

[Unco]

It equals \(\displaystyle \frac{\, \sqrt{5} \, }{ \, 2 \, }\), not 0.25. . .