# Simplify an expression with ArcCos [closed]

How can simplify this expression with Mathematica ?

Sin[1/2*ArcCos[x]]^2


Thank you for your help

## closed as off-topic by Bob Hanlon, m_goldberg, user9660, Sjoerd C. de Vries, MarcoBDec 28 '15 at 0:14

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• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – Bob Hanlon, m_goldberg, Community, Sjoerd C. de Vries, MarcoB
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Sin[1/2*ArcCos[x]]^2 // TrigReduce

• Alternatively (but not as succinctly), Sin[1/2*ArcCos[x]]^2 // TrigToExp // Simplify – Bob Hanlon Dec 27 '15 at 15:26