code: function(ratio, opt) {
  
          if (ratio <= 0) return this.divideAtT(0);
          if (ratio >= 1) return this.divideAtT(1);
  
          var t = this.tAt(ratio, opt);
  
          return this.divideAtT(t);
      }
docs: Divides the curve into two at requested `ratio` between 0 and 1 with precision better than `opt.precision`; optionally using `opt.subdivisions` provided. For a function that uses `t`, use Curve.divideAtT().