Basic iPhone math app

Hi, I would like this app to be only 1 page, with a small .jpg at the top. The page should have 3 'text boxes' in which you can enter numbers (so when clicked on the number keyboard should come up.) Only 2 boxes will be filled with numbers at any one time. The math that is applied to those two numbers and also depends on which two boxes are filled. The result of the math applied's value would be put in the third box. Below is the logic for it. (a - number in box 1, ? b- number in box 2, ? ? c- number in box 3) if Box 1 & 2 filled then Box 3 = 2a*sin(b) if Box 1 & 3 filled? then Box 2 =? 1a*cos(c) if Box 2 & 3 filled? then Box 1 =? 2b*sin(a) Feel free to email with questions!