Cos3theta=1

Question

Find all Solutions if 0 degrees is less than or equal to Theta is less than 360 degrees. 

Cos 3theta=1

Answer 1

cos(3θ) = 1

 

3θ = k(360°), k = 0, ±1, ±2,...

 

θ = k(120°)

 

Solutions where 0°≤θ<360°:  θ = 0 (when k=0), θ = 120° (when k=1), θ=240° (when k=2).

 

Answer 2

Hi Lexie,

 

cos 3theta = 1

then 3theta = 0 andr 3theta = 2pi

theta = 0  and theta = 2pi/3

theta = (0, 2pi/3)