Although the default is a 3-4-5 right triangle, you can make an adjustment so that you can do equilateral, isosceles, or scalene triangles. What sets this apart from similar apps is that it provides an explanation for every problem done. You can also save your triangles. So this is a triangle solving app with explanations. One use I see for this is to help students see how the triangle inequality theorem works. If you enter three values that do not make a triangle, it will let you know why it is not a triangle.
I like that it provides an explanation on why it does not work. I also like the program allows you to see the use of the pathagorean theorem or the law of cosines to find missing values. I can use this in two or three classes so students can check their work and get an explanation.