just wondering why the "plus or minus" is not on the tan ?
Consider when tan(x/2) is positive - it's exactly when x is between 0 and pi, or 2pi and 3pi, or… Consider when sin(x) is positive - it's exactly when x is between 0 and pi, or 2pi and 3pi, or… And 1+cos(x) is always positive.
Consider when tan(x/2) is positive - it's exactly when x is between 0 and pi, or 2pi and 3pi, or… Consider when sin(x) is positive - it's exactly when x is between 0 and pi, or 2pi and 3pi, or… And 1+cos(x) is always positive.