The Casio fx-991ES<\/em> NATURAL DISPLAY<\/span> is, in my opinion, comparable to a Sharp WriteView<\/em>. Their screens are deeper than most scientifics, so that they can display fractions up-and-down. They can also simplify radicals symbolically, like you would by hand: √(40) will display as 2√(10) (in the right mode). Moreover, they can display radian measures symbolically, using pi: sin^(-1)(0.5) will display as π\/6 (in rad mode). Sharp summarizes these features as WriteView<\/em>; Casio describes them as NATURAL DISPLAY<\/span>. <\/p>\n Those features I will explore in other posts; today I’m showing, with an example, how one might use the equation solver built into the Casio fx-991ES<\/em>. It’s surprisingly powerful, and surprisingly easy to use:<\/p>\n Example<\/strong>: Solve 11xe^(-0.44x)-1.2sinx + 5 =0<\/p>\n This is likely not an equation most people want to tackle by hand. Here’s how to do it with the Casio fx-991ES<\/em>:<\/p>\n Step 1: I was in COMP mode to use the solver. That’s MODE 1<\/span>. Also, I was in rads<\/strong>(Shift Mode 4), which is important: sinx is in the equation.<\/p>\n Step 2: You need to enter the equation as Y=11Xe-0.44X<\/span><\/sup>-1.2sinX+5<\/span>. Important: to enter the =<\/span> in the equation, use alpha calc<\/span>.<\/strong> Use the alpha<\/span> switch to enter the Y<\/span> and the X<\/span>.<\/p>\n Step 3: After you’ve entered the equation, key in shift calc<\/span>.<\/p>\n Step 4: Y?<\/span> should now appear. Key in 0<\/span>, then regular =<\/span>.<\/p>\n Step 5: Solve for X<\/span> should now appear. There may already be a number across the bottom; regardless, press regular =<\/span>.<\/p>\n Step 6: The screen may go blank for a few seconds while the solver works. Soon, though, you’ll be greeted with the solution (if the equation was, indeed, solvable:)). There will be three lines:<\/p>\n To double check, I fed the same equation to the solver on my old Sharp EL-520W; it agrees exactly with the Casio’s solution:)<\/p>\n Have fun experimenting!<\/p>\n\n