Each year the manufacturers of calculators change their design and I try to evaluate which $20.00calculator will best fill the student's needs for TELA, TELC, TEL3, TEL4, TEL5 and TEL6.  Shown below is the TI36X solar calculator. Price, at Staples, is $19.99.  If you have a Graphing calculator, you will have to pay your dues and learn how to use it to do the Polar to Rectangular and R--> P conversions.  This unit is easy!  Also the BIN, HEX, OCT and DEC conversions are also simple on this calculator.  Find the exact TI36X, similar numbers  are NOT THE SAME.