In = function (v)
{
    if (v === 0)
    {
        return 0;
    }
    else if (v === 1)
    {
        return 1;
    }
    else
    {
        return 1 - Math.cos(v * Math.PI / 2);
    }
}
Sinusoidal ease-in.

@function Phaser.Math.Easing.Sine.In
@since 3.0.0

@param {number} v - The value to be tweened.

@return {number} The tweened value.