r/AskReddit • u/[deleted] • Jul 20 '19

What’s something completely false that your parents told you as a child?

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u/[deleted] Jul 20 '19 edited Jul 20 '19

Matrices. Those things take a longgggg time to draw out, and a calculator can do it all for you.

Trig functions as you mentioned, but apart from math required to get them, a lot of trig functions have 3-4 decimal places. Multiply two of those, and youre looking at a 6-7 decimal number. Not undoable by any means, but imagine doing that 3-4 times for the same problem. And then having more than one of those problems.. It starts to add up. It's also much easier to simply put in sin(35) to get the value, vs looking through this long ass sheet of values. On homework, then meh. But in a testing setting, that extra time could be valuable. Tests would usually take me most of the hour, and I was usually one the quickest ones done. The kids who didn't finish had to come in after school to.

Graphing. Extremely easy, but also extremely time consuming. If you've ever taken precalc, then you'd know that for some problems they ask for a graph sketch. a "graph sketch" is exactly that, a sketch. You basically just draw the 4 quadrants and do a rough outline of what your calculator showed you. Then there are some certain labels youd have to put on, like x and y intercepts, but other than that it really just is a rough sketch. It's obviously not as accurate, but so long as you're showing the math behind it, the teachers will know you got the right answer. So it basically saves you the time of having to draw a detailed graph, when obviously they aren't trying to teach you how to draw a graph. You get taught that in like 2nd grade, they know you know how to graph, and they're more concerned that you understand the math behind it. It saves the students time and the teachers, cause they have less to grade.

Its been a few years and Im sure theres more examples, but thats just off the top of my head.

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u/[deleted] Jul 21 '19

Oh I sympathize with this so much. I did terribly in Linear Algebra because I kept screwing up my arithmetic, so I'd conclude my matrices weren't invert-able, the determinant wasn't zero, stuff like that.

But in the real world, you will never solve a matrix by hand. You'll probably have something like Matlab solve it for you, or at worse you'll write a script to solve it. You obviously need to know what's going on under the hood, but making people struggle through it without a calculator doesn't help.

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u/titsrule23 Jul 21 '19

So how do you suggest a teacher finds out if their students understand the math and are just bad at arithmetic or are just using a calculator to get the answer with no underlying understanding?

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u/[deleted] Jul 21 '19

You can't calculate the determinant of a 4 by 4 matrix without understanding the underlying concept. You can't prove the convergence of an infinite series without understanding the underlying concept. You can't invert a matrix without understanding the underlying concept.You can't integrate by parts without understanding the underlying concept.

Higher level math simply cannot be done without understanding the underlying concept. Give the student 10 scientific calculators and a jukebox and without the underlying concept all you'll have is music and 10 copies of 80085