code: func MercatorScaleFactor(degreesLatitude float64) float64 {
  	if degreesLatitude < -90.0 || degreesLatitude > 90.0 {
  		panic(fmt.Sprintf("geo: latitude out of range, given %f", degreesLatitude))
  	}
  
  	return 1.0 / math.Cos(degreesLatitude/180.0*math.Pi)
  }
docs: // MercatorScaleFactor returns the mercator scaling factor for a given degree latitude.