HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 301

Step4. Because I know that part (iv) of the question requires me to re­ use these extremum values in an integration (which I would like to be as accurate as possible), I am going to 'save' the extremum value just found. I change into the HOME view and store it as shown in memory A. Note: You MUST store the point of interest before moving the cursor in the PLOT view. As soon as the cursor moves its new position over-writes the extremum value. If you want the y coordinate, just evaluate F(X). Now use the Extremum tool again to find and store the x coordinate of the second turning point into memory B as shown. Step 5. The PLOT view shows that part of the area we require for part (iv) is negative, so we need to know the x intercept between the two turning points. Fortunately we know from Step 2 that it is the point (2,0). If we did not know this already, then we could use the menu again, retrieving this time from the VAR menu the variable called 'Root' and perhaps storing that into memory C. We will evaluate the integral in the HOME view where you can use the accurate values you stored in Step 4. It needs to be done in two parts and added (subtracted actually to reverse the sign of the negative part). This is shown right, with the key having been used to add the values. 301