In the above figure, you just select the input boxes for the known items and press the "Calculate" button.
Before calculation, hovering the mouse over any input will indicate valide ranges.
After calculation, hovering the mouse over the calculated values, will splash the formula.

The rules are:
1) It is possible to calculate angle A if angle B is known or the opposite.
2) It is possible to calculate all unknown figures if a) one angle (A or B) and one side is known or b) two sides.