Best graphing Calculator is 3d graphing calculator. http://riskofradiation.com/instruments/best-graphing-calculator-is-3d-graphing-calculator/
3d graphing ability may be required depending on the subject or research one is taking. This is the ability for the graphing calculator to produce graphs of multivariable functions (over the XY Z) instead of only the Cartesian XY plane. This is required in classes such as multivariable calculus and linear algebra. However if you are taking elementary algebra or trigonometry you don’t need this capability. One of the best 3d graphing calculators is the TI89 .
The best place to buy the – the TI89 Titanium is on Amazon.