void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
    int x1 = 1;
  int y1 = 0;
  int x2 = 37;
  int y2 = 6;
  float yd = ((float)y2 - (float)y1) / ((float)x2 - (float)x1);
  // float yd = (y2 - y1) / (x2 - x1);  // this does not work
  Serial.print("yd: ");
  Serial.print(yd, 4);
  Serial.print("(y2 - y1): ");
  Serial.print((y2 - y1));
  Serial.print(", (x2 - x1): ");
  Serial.print((x2 - x1));
  Serial.print(", ((float)y2 - (float)y1) / ((float)x2 - (float)x1): ");
  Serial.println(((float)y2 - (float)y1) / ((float)x2 - (float)x1), 5);
  }

void loop() {
  // put your main code here, to run repeatedly:

  delay(10); // this speeds up the simulation
}