To find the angle that is halfway down from a position, you would typically calculate the position from which you are starting.
If you consider a full rotation, which is 360 degrees, halfway down would be at 180 degrees. This means that if you start at 0 degrees (the positive x-axis), going halfway down would involve a rotation of 180 degrees to the negative y-axis.
If you meant "halfway down" from another specific angle, please provide that starting angle for a more detailed answer.