Question

Cos (2x) = √3/2
Solve the equation on the interval [0,2pi)

Answer 1

Explanation:

sqrt(3)/2 = cos(pi/6)

therefore,

2x = pi/6

x = pi/12

that means in the interval of [0, 2pi) there is a second solution : pi/12 below 2pi

x = 2pi - p/12 = 23pi/12

so, the solutions are

x = pi/12

or

x = 23pi/12

in other words x = 15° or 345°.