Hello, everyone. Tom from everystepcalculus.com and everystepphysics.com. With regard to a curl, there are 2 notating systems. One, PQR and MNP. Why they chose those letters, I have no idea, in math. But that’s the way it is. Some professors use one and some professors use the other. Sometimes they use the Cartesian system which is I, J, and K, also. So I’m going to do an M, N, P system right now. Just throw in arbitrary functions and show you. Index 8 to get to my menu. We’re going to go down here to curls. We’ll go down to M, N, P. I like to, I’m going to just show you the definition of a curl, first. Curl is a vector with a magnitude (length) and direction. It represents the circulation, rotation, twist, or turning force per unit area of a field. Now that’s the best definition I can come up with because I asked that to a lot of times in calculus. I said, what the heck is this, what are you talking about? And even this, I hesitate to believe that it has any value other than some mathematical nonsense that they throw around in calculus to do these problems. A vector field is a three dimensional blob and many small vectors pointing in different directions together forming a pattern of definite form. Curl equals Twist divided by Area. A curl of F (x,y,z) is equal to the, here’s the M N P system and here’s the P Q R system defined within the Cartesian coordinates I J K. And if you’re to use the vector notation, you have these arrows on the side. M, N, P and you have arrows on the P, Q, R system. M, a function (x, y, z) in i direction. N a function (x, y, z) in j direction, and P a function (x,y,z) in k direction. Or used also is P, Q, R, etc. So now let’s do an example. We’re going to choose number 2, MNP. You have to press Alpha before you enter anything into these entry lines, here. Alpha 2 times Y squared times Z. Alpha 5 times X times Y times Z. Now these functions, I’m just dreaming up so. It’s probably going to go off the calculator. The answers. Because the screen is so small. It doesn’t go off the calculator screen on the TI-92 plus but it doesn’t on the Titanium. And then I know that you’re doing homework or experimenting because anytime an equation goes off the, think of it. The rest of your class is scored by partial credit and the class curve. Who else in the class could solve a deep problem in calculus. So will never be on a test because it’s just too hard. You would take too much time. Even if you could solve it, it would take too much time, too much paperwork, there would be no time for the rest of the problems on the test. And I have to program for tests only because of the space of the Titanium for memory use and just sanity. There’s ten million derivations of calculus derivatives and integrals. In each one of these, I have to do on a piece of paper, every one of them, to find the correct step by step process. Once I get done with that, I say it’s the best system for solving a problem but it might not be the system that your professor uses on the blackboard so you want to keep that in mind, too. Here’s the second one for the P. I’m going to put in, let’s put in Y cubed times z squared times X. oh, I didn’t press Alpha first. So we need to go back and change it. So alpha 2 times X squared times Z. Alpha 3 times 5 times X times Y squared. Alpha Z cubed. Now they seem to be correct. I’m going to say okay. Choose number 1. Here’s the matrix system for solving the curl and it’s really a cross product system. I don’t know who can remember this. I can’t, I couldn’t. That’s the reason I programmed it. Why try to memorize something when you can actually program it and have it for the rest of your life? So here’s the answers to what’s going on. With partials with respect to certain other partials. Oh the answer turned out to be not too bad, here. So now we can compute it at a point. Choose number 3. Enter the points, let’s just enter some. Alpha 1, alpha minus 5, alpha 9. Again, I show you what you’ve entered. And you substitute. These would be parentheses on your paper. These quotation marks have to be done in the programming, I can’t do anything different. And it’s substituting 1 for any X or minus 5 for any Y or 9 for any Z in the answer here. Here’s a Y right here, minus 5 but you put parentheses around that because you’re substituting. And the answer turns out to be 377. Pretty neat, huh? Have a good one.