Update textbook.fr.md

12.temporary_ins/44.relativity/40.n4/10.special-relativity/07.coherence/textbook.fr.md

@@ -39,12 +39,12 @@ ds^2&=c^2 dt^2- dx^2- dy^2- dz^2\\
 $`x^0=ct\;;\;x^1=x\;;\;x^2=y\;;\;x^3=z`$
 
 $`\begin{align}
-ds^2&=(dx^0)^2 -(dx^1)^2 -(dx^2)^2 -(dx^3)^2\\
+ds^2 &=(dx^0)^2 -(dx^1)^2 -(dx^2)^2 -(dx^3)^2\\
 &=(dx^0')^2 -(dx^1')^2 -(dx^2')^2 -(dx^3')^2
 \end{align}`$
 
 $`\begin{align}
-ds^2=\big(dx^0\big)^2 -\big(dx^1\big)^2 -\big(dx^2\big)^2 -\big(dx^3\big)^2\\
+ds^2 &=\big(dx^0\big)^2 -\big(dx^1\big)^2 -\big(dx^2\big)^2 -\big(dx^3\big)^2\\
 \\
 &=g_{ab}\;dx^a dx^b
 \end{align}`$