Not very user friendly (updated)
Despite the efforts of the developer and excellent graphics which adjust to show the resulting shape of the triangle, this app does not work intuitively.
Consulting 'help' only helps a little because some of the descriptive terminology is unclear. For instance, when I tried clicking the grey frame as (I thought?) I was being instructed, nothing happened. Also, I could not find a way to get the app to display decimals in the angles which appear to be being rounded to the nearest degree, despite seeing an example with decimals. I found no way to alter the default setting for increased accuracy.
I feel a lot of potential for this app but it's a shame it does not use a generic triangle, transforming according to minimum input without the need to first make a selection from the top bar and then ensure subsequent instructions are correctly followed.
Response from developer
Thank you for using my app. You can change an angle or side by tapping a grey frame. (A line of the tappable frame is thick.) Also you can change number digits from "Digits" menu on bottom of triangle. I will be able to help you. If you have any questions, please feel free to contact me by email. You can send me a email from "App Support / Contact" on App Store.