Question

Solve "cos 3x = -1" algebraically given the domain [0,2pi)

Answer 1

\[0\le x <2\pi\]

Answer 2

so 3x = cos^(-1) (-1)

then 3x = pi so x = pi/3

cos is negative in 2nd and 3rd quadrants


2nd is pi - pi/3 3rd is pi + pi/3

then \[x = 4\pi/3, 2\pi/3\]