Answer:
x=π/9+2πn/3, 5π/9+2πn/3, for any integer n
Step-by-step explanation:
Given:
cos3Ф=1/2
taking inverse cosine on both sides
cos^-1(cos3Ф)= cos^-1 (1/2)
3Ф=π/3
Ф=π/9
for second solution, subtracting π/3 from 2π
3Ф=2π-π/3
= 5π/3
Ф=5π/9
here period of the function is 2π/3
Hence the value of cos3Ф will repeat after every 2π/3
x=π/9+2πn/3, 5π/9+2πn/3, for any integer n !
