%% trigonometrie, valeurs remarquables $$ \vcenter{ \def \trait{\noalign{\hrule}} \offinterlineskip \halign{ \tv height 17pt depth 10pt \hfq $\displaystyle #$\hfq \tv && \hfq $\displaystyle #$\hfq \tv \cr \trait x& 0& {\pi \over 6}& {\pi \over 4}& {\pi \over 3}& {\pi \over 2} \cr \trait \cos x& 1& {\sqrt3 \over 2}& {\sqrt2 \over 2}& {1 \over 2}& 0 \cr \trait \sin x& 0& {1 \over 2}& {\sqrt2 \over 2}& {\sqrt3 \over 2}& 1 \cr \trait }}$$