Question: trigonometric solve without floats


I'm trying to solve this trigonometric equation:

e := 4·cos(t)+2·cos(2·t)=0. In the interval 0..2·Pi

However when i try: 

solve([e, 0 <= t <= 2 Pi], t, AllSolutions, explicit)

I won't give my a straight answer.

I have also given Student:-Calculus1:-Roots a try:

Student:-Calculus1:-Roots(e, t=0..2·Pi)

But it will only give me an answer when i use the numeric option. With I do not prefer.

How to I solve the equation without getting a float answer.

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