The trailing edges would be higher but not by as much as you're thinking. You can't add the angles directly like you are doing.
The vertical height from an angle like this is related to a function of the angle times the horizontal distance. And for the two angles you don't add the angles. Instead you need to calculate the vertical height for that horizontal run and angle for the two cases then add the verticals together.
If we're talking trigonometry the rise related to the angle change is the sine function of the angle times the length of the lower side or, in this case, the span or chord depending on which you are looking at.
The sine of 2° can be found by using the Scientific mode of the calculator that comes with Windows. The value in this case for 2° is 0.035. So the rise at the trailing edge due to dihedral is .035 x the span of the one side. The additional rise due to your 2° of washout is .035 x the tip chord if you set the dihedral at the leading edge to 2°. Or if you set the dihedral at the main spar to 2° then it'll be .035 times the distance from the spar to the trailing edge. Add the rise from the panel's span to the additional rise from the washout and you get your total added rise at the tip of the trailing edge.
To go backwards from the added vertical heights to find the angle of the trailing edge in degrees gets a little more iffy. How we know the tip vertical and the half span lengths. To find the resulting angle we need to do a reverse or inverse "tangent". In trigonometry this would be the vertical length divided by the horizontal panel span then do an "arctan" on the resulting value to get the dihedral angle of the wing's trailing edge.
Which right about now is likely more than you wanted to know, right?
