Question: Simplifying trig function within a procedure

I've made a procedure to fin the real roots of 2x³-4x²-22x+24, my result gives me:

2x³+(-4x²)+(-22x)+(24) has three real roots:

2/3371/2sin(1/6Pi+1/3arccos(55/1369*371/2))+2/3,

-1/3371/2(sin(1/6Pi+1/3arccos(55/1369371/2))+31/2sin(1/3Pi-1/3arccos(55/1369*371/2)))+2/3,

-1/3371/2(sin(1/6Pi+1/3arccos(55/1369371/2))-31/2sin(1/3Pi-1/3arccos(55/1369*371/2)))+2/3

when it should say 4,-3 and 1, I've tried simplify and evalf only gives me the approximate answer, can anybody suggest what to do?

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