Change math symbol from $$ to \[\]

Author: aliphys

content/hardware/01.mkr/01.boards/mkr-wifi-1010/tutorials/mkr-battery-app-note/mkr-battery-app-note.md

@@ -64,7 +64,7 @@ The nominal voltage of both LiPo and Li-Ion batteries is around 3.7V and is comm
 
 In the MKR boards, the battery terminal is connected to the SAMD21 via a reserved pin (PB09) known as `ADC_BATTERY` within the Arduino Core. This pin is used internally on the board, and is not accessible via the MKR pins. Since the voltage of a Li-ion battery exceeds 3.3V (the AREF value), a voltage divider must be used to extend the range while also ensure that only safe voltages are applied to the microcontroller. We can calculate the output voltage using the following formula
 
-$$ V_{out} = \frac{V_{source} \times R2} {R_1 + R_2} $$
+\[ V_{out} = \frac{V_{source} \times R2} {R_1 + R_2} \]
 
 In the MKR WIFI 1010, $R_1$ and $R_2$ are 330k ohm and 1M ohm respectively. Therefore, for a resolution of 12 bits, the board is subject to 3.3V that corresponds to about 4.39V on the battery side. Therefore, we can cover the operating value of a whole battery. The high values reduce the leakage current that may pass through, increasing the life of the battery. The capacitor acts to clean the signal.