text: var pi = Math.PI,
      halfPi = pi / 2;
  
  export function sinIn(t) {
    return 1 - Math.cos(t * halfPi);
  }
  
  export function sinOut(t) {
    return Math.sin(t * halfPi);
  }
  
  export function sinInOut(t) {
    return (1 - Math.cos(pi * t)) / 2;
  }
  