Servo 90 degrees sliding with ultrasonic sensor

// Include the Servo library
#include <Servo.h>
// Declare the Servo pin
int servoPin = 3;
// Create a servo object
Servo Servo1;
int trigPin = 11;    // Trigger
int echoPin = 12;    // Echo
long duration, cm, inches;

void setup()
     {
        // We need to attach the servo to the used pin number
        Servo1.attach(servoPin);
        pinMode(trigPin, OUTPUT);
        pinMode(echoPin, INPUT);
        Serial.begin(9600);
     }

void loop()
     {

        // The sensor is triggered by a HIGH pulse of 10 or more microseconds.
        // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
        digitalWrite(trigPin, LOW);
        delayMicroseconds(5);
        digitalWrite(trigPin, HIGH);
        delayMicroseconds(10);
        digitalWrite(trigPin, LOW);
        // Read the signal from the sensor: a HIGH pulse whose
        // duration is the time (in microseconds) from the sending
        // of the ping to the reception of its echo off of an object.
        pinMode(echoPin, INPUT);
        duration = pulseIn(echoPin, HIGH);
        // Convert the time into a distance
        cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343
        inches = (duration/2) / 74;   // Divide by 74 or multiply by 0.0135
        Serial.print(inches);
        Serial.print("in, ");
        Serial.print(cm);
        Serial.print("cm");
        Serial.println();

    if (cm < 50 )
      {
        for(int i = 45; i <= 135; i=i+2)
           {
              Servo1.write(i);
              //Serial.println(i);
              delay(50);
           }
        for(int i = 135; i >= 45; i=i-2)
          {
              Servo1.write(i);
              //Serial.println(i);
              delay(50);
          }
      }
    }