flow like the river

BACK_BACK/node_modules/d3-ease/src/sin.js

@@ -0,0 +1,14 @@
+var pi = Math.PI,
+    halfPi = pi / 2;
+
+export function sinIn(t) {
+  return (+t === 1) ? 1 : 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;
+}