The concept you've used for a sine wave seems strange. In a sine wave the equation is
y=sin(x);
This should work for a sine wave
mSpeed=constant;
mTargetX = constant2;
mOriginalX=constant3;
mDistanceX=mTargetX-mOriginalX;
Now in the repeatedly called onDraw
mPositionX+=mDistanceX/mSpeed; //Distance divided by speed
mPositionY=(float) (0.5* Math.sin(Math.PI*(Math.abs(mPositionX-mOriginalX))/mDistanceX);
//Assuming you want it to go to pi degrees
//Divide current distance by total distance * total angle reqd