https://learn.microsoft.com/en-us/dotnet/api/system.windows.media.animation.elasticease.easeincore?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0
ElasticEase.EaseInCore(Double) Method (System.Windows.Media.Animation) | Microsoft Learn
Provides the logic portion of the easing function that you can override to produce the EaseIn mode of the custom easing function.
windows mediadoublemethodsystemanimation