How do you solve 2cos^2x-1=0?

Question

This is a trigonometry identity equation. 

Answer 1

2cos^2x-1=0

2cos^2x=1

cos^2x=1/2

cosx=±√(1/2)

√(1/2)=1/√2=√2/2

cosx=±√2/2

x=∏/4=45º for √2/2

x=7∏/4=315º for √2/2

x=3∏/4=135º for -√2/2

x=5∏/4=225º for -√2/2