CalcPad X 1.1
This lets you type in a mathematical expression, edit it for accuracy, format it for readability, and evaluate it with a single mouse click or keystroke.
And, because it takes full account of standard use of braces and mathematical hierarchies, you can type the expressions exactly as they're written.
Each mathematical expression can be saved for later use. Plus, you can use variables to evaluate the same expression with multiple values and rename variables for clarity and readability.
Many scientific and trigonometric functions are included.
OS X 10.2.x