calculati sin²(x+pi/2)+sin²(x+pi), x€R
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sin( x+π/2 )=sin( π/2 +x )=sin( π/2 -(-x) )=cos(-x)=cos x ;
sin( x+π)=-sin x ;
sin²( x+π/2 ) +sin²( x+π )=cos²x +sin²x=1 (unde x∈R).