WHILE IT'S NOT THE CHEAPEST OR THE EASIEST CALCULATOR, IT IS THE BEST.

As a sophomore, my high school splurged and purchased TI-92 graphing calculators for the lot of us. While coming from a TI-83 background made it difficult to use the new interface, I was amazed at the power. Solving algebraic equations, factoring, computing derivatives, and integrals had never been so easy. However, due to the TI-92's QWERTY keyboard layout, it was not allowed on such standardized tests as the ACT, SAT, AP tests, etc. TI's response? The TI-89.

This calculator features all the amazing features of the TI-92; it's merely flipped vertically to resemble the other 80-series TI calculators. The letters are all there, merely hidden behind other buttons requiring one to press an "alpha" button to allow access to the entire alphabet. This (and the TI-89 titanium) is definitely TI's most powerful calculator. Plus, the TI-89 can be used on all AP tests, the SAT, the ACT, and all of the upper level math courses I've taken.

Ease of Use
Because the TI-89 is a departure from the earlier TI-80-series, the new interface can be difficult to get used to. It is the first calculator that treats a variable as a true variable. For example, if you type in “solve(x=(1+1/y)^y,y)”, the calculator will be able to solve for “y” and tell you what it equals. It can solve inequalities, factor, calculate integrals and derivatives, etc. However, this basic change in how the calculator functions required a change in the entire interface. Therefore, I would recommend this calculator only for those who are willing to take the time to learn how to use it. There is a very steep learning curve involved.

Interface
While the new interface is difficult at first, it doesn't take long to realize the more difficult interface empowers the TI-89 to go places no other TI has gone before. Complete with drop down menus, cut, copy, and paste commands, as well as a CPU-esque blinking cursor, TI is definitely taking steps in right direction of integrating calculators with computers. Also, if you download the new updated operating system (using a USB cable), it comes with a new menu. complete with icons, time and date, and other additional features.

Battery Life
The TI-89 runs off of 4 AAA batteries. This may seem like a lot; however, the batteries last for a long time. Even while using the calculator for hours daily, I still only had to change the batteries once every 3-4 months. The 89 also comes with a backup battery (a standard watch batter), which means you won't lose your information even while changing the batteries.

Display Screen
The LCD viewing screen is much improved over the previous TI-80-series calculators. The viewing screen is a only slightly larger, but the resolution is much higher (it has about the same degree of clarity as a palm pilot). This means more numbers and letters can fit on the screen than ever before, which makes life much easier for you. The contrast is fully adjustable, and the screen is viewable with very bright or very dim lights. Also TI has added a neat feature called pretty print. This means if you put in a long equation with powers, roots, logs, etc., the calculator will make it look like how you would write the equation on the page. This makes it much easier to see if you've made any errors.

Graphing
In terms of graphing capabilities, TI has definitely taken leaps and bounds with the 89. The 89/92 calculators are the first to offer 3-D graphs. However, it takes a lot of time to graph it, and only one tri-variable function can be shown at once. Still it is a big help and a huge step for handheld graphing calculators. The standard 2-D graphs are much more powerful and easier to use before. Also, with the improved viewing screen, the graphs are much smoother. This makes the graphs far more accurate. Another neat addition is the ability to draw tangent lines off any point in the graph of a function and to shade the area under, over, or between graphs.

Other Programs
TI is continually improving on their product by offering downloads for the calculator. All that's needed is an internet connection, USB port, and a connection cord. Need a calendar? How about a daily planner? Some reading material? With the TI-89's nearly 1 MB of total memory, entire books can be placed on the calculator, along with your daily schedule and other useful applications. If you're into playing games between work and study, the TI-89 offers the highest quality games for any calculator out there. The TI-89 can become your palm pilot.