OK, so maybe this is overkill, using SolidWorks to determine the outside dimensions of acute and obtuse bends. Why not use a tool that makes your job easier? I know 

there are a few tools around that simplify making these measurements while fabricating precision sheet metal, we didn't have one back in the mid to late 80's.

In making the AutoCAD fabrication drawings for the shop I made another one so my brake guys could easily and accurately check their setups and bends using this trick.

The 'trick' if you want to call it that is using a dowel pin that is greater in size than the bend radius, times 2 of course. This allows you to nestle the pin into 

the radius created by the bend and use the butt edge of a Vernier caliper to the edge to make the resulting measurement.

This works even when the radius is not perfect though your bend allowance/deduction methods must accommodate your bending practices.

What would be important here is to have your bend angle accurately formed and verified before using this method.

Another important consideration is how you or your customer dimensioned these angle bends or how you may have slightly changed the bend radius to accommodate your 

stock tooling. I tried to accommodate the Flange Dimension styles offered by SolidWorks to make this easy to use.

If your customer dimensioned to the centerline of their specified bend radius, you would obtain that outside dimension from this tool. The Tangent Measure file referenced here allows you to determine both acute and obtuse dimensions at once, it is possible to cause this tool to 'crash' by entering bend angles less than zero or greater than 90 degrees. It might be a good idea to make this file write protected or keep another copy around as a backup in case that happens.

Let's get to using it....

Open the file and you're presented with a simple dimensioned feature with two bends, one acute and one obtuse. You can simply 'double-click' on Bend Angle, Bend Radius 

or Check Pin Diameter and change those dimensions to match yours. Then just click on the rebuild icon to update the changes. You cannot change the material thickness 

here though.

If you need to change the material thickness just go to your Configurations Tab and Edit the Design Table. Actually you can change all of the dimensions here if you like. Click outside the Design Table and SolidWorks will recalculate the dimensions and display the model again.The dimensions calculated and displayed for you will allow you to 'adjust' the inspection dimensions so your brake guys can accurately measure the bends on the shop floor.

It might be a good idea to make a print just for those dimensions. I can't tell you how many times I've seen brake operators 'eyeball' the dimensions to 'get' what they need.

Feel free to improve this tool and add your information into the Summary Information tab in properties and please repost it.

I am not including information on how you might include bend dections or allowances here, it seems there are more than a few ways these are done. This method can be used regardless.

Hope this helps!