well, you know that cos π/6 = √3/2
So, with the negative value, you have
x/2 = 5π/6 or 7π/6
Solve this multiple-angle equation.
cos x/2 = -(sqrt3)/2
4 answers
So the solutions are also 5π/6 + 2npi and 7π/6 2npi, right?
nope. cos(x/2) has period 4π
also, note that x/2 = 5π/6. So, x = 5π/3.
Watch the details, guy.
Watch the details, guy.