Use it just like a normal calculator! For the trig functions and square root, you need to press the black key before you input your value. In the top row of black buttons: S = sine, C = cosine, T = tangent, A = previous answer. The red C in the second row is the clear button.
Everything is pen except for the variables that show the input/output. UPDATE LOG: July 5 2017: Curated by @nickeljorn! June 7 2017: Converted calculator to pen Jan 27 2017: Added decimal point, negative sign, and answer key Jul 12 2016: Added square root and trig functions Jun 14 2016: Released
