diff --git a/TST_sti2d/02_Derivation/1E_vitesse.pdf b/TST_sti2d/02_Derivation/1E_vitesse.pdf
index 0ff661c..39fb8bc 100644
Binary files a/TST_sti2d/02_Derivation/1E_vitesse.pdf and b/TST_sti2d/02_Derivation/1E_vitesse.pdf differ
diff --git a/TST_sti2d/02_Derivation/exercises.tex b/TST_sti2d/02_Derivation/exercises.tex
index f17bbaf..c76f895 100644
--- a/TST_sti2d/02_Derivation/exercises.tex
+++ b/TST_sti2d/02_Derivation/exercises.tex
@@ -10,7 +10,7 @@
         \tkzInit[xmin=0,xmax=14,xstep=1,
         ymin=0,ymax=4000,ystep=500]
         \tkzGrid
-        \tkzDrawX[label={$t$},above=0pt]
+        \tkzDrawX[label={$t (s)$},above=0pt]
         \tkzDrawY[label={$Distance (m)$}, right=2pt ]
         \tkzLabelX
         \tkzLabelY
@@ -24,7 +24,7 @@
         \tkzInit[xmin=0,xmax=14,xstep=1,
         ymin=0,ymax=200,ystep=20]
         \tkzGrid
-        \tkzDrawX[label={$t$},above=0pt]
+        \tkzDrawX[label={$t (s)$},above=0pt]
         \tkzDrawY[label={$Hauteur (m)$}, right=2pt ]
         \tkzLabelX
         \tkzLabelY