The discussion revolves around proving a trigonometric identity involving cosine functions, specifically the equation 1 + cos(2π/5) = 2 cos(π/5). Participants are exploring the validity of this identity and its implications.
The discussion is active, with participants exploring different interpretations of the identity. Some guidance has been offered regarding the use of double angle identities, but no consensus has been reached on the proof itself.
Participants are working under the assumption that the original identity may be incorrect, leading to discussions about alternative forms and the need for clarification on the problem statement.
hms.tech said:Homework Statement
Show that :
1 + cos(2∏/5)= 2 cos(∏/5)
Hello sacscale. Welcome to PF !sacscale said:Looks like the identity should have been:
1 + cos(2∏/5) = 2 cos^2(∏/5)
Assuming you are trying to prove 1 + cos(2##\pi##/5) = cos2(##\pi##/5) rather than what you originally posted, rewrite the left side using the double angle identity.hms.tech said:Yes but the issue remains, how do we prove it ?