Update README.md

README.md

@@ -40,11 +40,11 @@ $$  v_k = v_{k-1} + aT - \hat{a}_{k-1}T  $$
 
 displacement:
 
-$$  y_k = y_{k-1} + v_{k-1}T + {a \over 2}T^2 - {\hat{a}_{k-1} \over 2}T^2  $$
+$$  y _k = y _{k-1} + v _{k-1}T + {a \over 2}T^2 - {\hat{a} _{k-1} \over 2}T^2  $$
 
 displacement_integral:
 
-$$  z_k = z_{k-1} + y_{k-1}T + {v_{k-1} \over 2}T^2 + {a \over 6}T^3 - {\hat{a}_{k-1} \over 6}T^3  $$
+$$  z _k = z _{k-1} + y _{k-1}T + {v _{k-1} \over 2}T^2 + {a \over 6}T^3 - {\hat{a} _{k-1} \over 6}T^3  $$
 
 accelerometer bias: