3cos (5x/2-1)+2=0 по магите

Question

3cos (5x/2-1)+2=0 по
магите

Answer 1

Cos(5x/2-1)=-2/3
5x/2-1=+-(π-arccos2/3)+2πn
5x/2=1+-(π-arccos2/3)+2πn
x=2/5+-2/5(π-arccos2/3)+4πn/5,n∈z