(Cosx-1)^2=cos^2x-1

Question

(Cosx-1)^2=cos^2x-1

Answer 1

(сosx-1)²-(cosx-1)(cosx+1)=0
(cosx-1)(cosx-1-cosx-1)=0
-2(cosx-1)=0
cosx-1=0
cosx=1
x=2πn,n∈z