Apps for learning apps.

Yesterday, I mentioned looking at vector addition apps to use with my college prep class to help them as they learn the material.  The only free one I found, BabuVectorsHD had no instructions and was not intuitive.  I figured out how to draw an arrow but I could not figure out how to get the arrow exactly as I needed it so the directional section of the vector would be right. 

What you see if all that you get.  I found it difficult to actually draw the vectors with the correct length and angle.  This makes it too hard for my students who are learning vectors to use. 
I did a bit of looking and there are very few apps that actually deal with vector math instruction but I did find a couple of ones that show vector addition and subtraction and one for vector products.  I also found a combined algebra II/vector Algebra app that looks interesting and is only $1.99.
I think I am going to bite the bullet and buy three or four paid apps to see which one will meet the needs of my students.  I might need more than one depending on how they present the material to the students.  It seems as if there are so many apps for lower math classes but as you go higher in mathematics, there are fewer apps available.  Hopefully I will be able to report back on the apps come next week.