Solve the multiple-angle equation. (Enter your answers as a comma-separated list. Let n be any integer. Enter your response in radians.)

Question

sec 9x = 2

Answer 1

sec 9x = 2
cos 9x = 1/2
so 9x = π/3 or 5π/3

but period of cos 9x is 2π/9
so adding / subtracting any multiples of 2π/9 to an existing answer will yield a new answer

general solution:
x = π/3 + 2nπ/9 , 5π/3 + 2nπ/9