Fixed mistake

You need to call pinMode() before calling analogWrite();

Author: stefankaters

Language/Functions/Analog IO/analogWrite.adoc

@@ -36,7 +36,7 @@ Writes an analog value (http://arduino.cc/en/Tutorial/PWM[PWM wave]) to a pin. C
 
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-You do not need to call `pinMode()` to set the pin as an output before calling `analogWrite()`.
+You do need to call `pinMode()` to set the pin as an output before calling `analogWrite()`.
 The `analogWrite` function has nothing to do with the analog pins or the `analogRead` function.
 [%hardbreaks]