Homeschool Math Blog

Maybe many of you already know about this, but I feel I am behind times sometimes. :) Desmos is a fantastic free online graphic calculator. It is super easy to use, also. It starts drawing the graph while you're still typing! Users can save graphs... see for example this one: a function, its derivative, and tangent drawn to a point . You can change the function as you wish. I changed it a little bit, and this is what I got: Here's another example: Riemann sums that someone created. Again, you can change the function and other parameters. The graphs can also be printed, emailed, and embedded on web pages.There's lots you can do: parameters (with sliders), inequalities, piecewise functions... In fact, many users have used it as a drawing platform by creating a bunch of piecewise functions, and so they come up with pictures like this one:

I'm not real super interested in obesity or calculations of people's weights, fat levels etc. but I ran across something half interesting that might be of interest to you. It is a new way to measure obesity or if a person is underweight, normal weight, or overweight -- and it doesn't even use your weight in the calculation! Murray has blogged about it at New measure of obesity – body adiposity index (BAI) He also made a calculator for it that compares your "results" as far as BMI and this new index, BAI. This new index uses your height and a measurement around the hips, and it's still somewhat experimental in the fact that it hasn't been thorougly tested in all races. The formula is hip (cm) ------------- − 18 [height(m)] 1.5 The resulting number should be a close estimate to your body fat percentage. Just for the record, or if you are curious, I am of normal weight, and supposedly have about 29% body fat according to that calcu...

I found something really nice at Mathmom's. She has written an excellent piece about problems in math education in elementary grades. Her point of view is of classroom instruction, but it is still really relevant even for homeschoolers. Some excerpts follow. On calculators: But to be honest, as much as I hate calculator use in school, in this age of calculators and computers, efficiency at hand computation is not, IMO, the most critical math skill for kids to learn. I am NOT saying that it should be ignored, or that kids should be allowed to skip it, and just use calculators in class (see rant linked above). But it is not, IMO, the be all and end all of math education, nor is it a prerequisite, IMO, for studying anything else. What I consider even more important is a strong sense of number . I want kids who know immediately when the answer they got (either by hand computation or with a calculator) is way off. I want kids who have an instinctive understanding of the distrib...

You might not have heard about it, but there exists a blog carnival for math, too. I submitted my rainbow entry into the latest one. Not all of the entries there are higher math, by the way, such as MathMom's Calculator rant or Puzzler puzzled from JD2718. If interested, go check it out: Carnival of math, edition 17 !

I would like to know a simple activity that i could do with a grade 2 student, which involves using the calculator. Here are a few ideas. Hopefully they are of help. Add or subtract the same number repeatedly. For example, start with 5, subtract 1 several times, and let the child see what happens -- he/she will get to negative numbers! Similarly, ask the student to start with 40 and subtract 10 repeatedly. Some children will be surprised at the negative numbers they will see -- but many will be able to understand the basics of how they work, just from simple calculator activities like these.   Start with any 2-digit number and add 100 repeatedly. For example, starting with 17, your 2nd grader will see the sequence 17, 117, 217, 317, 417, and so on. Start with a 3-digit number and subtract 50 repeatedly. Again, you will get a definite pattern. Ask the students to come up with their own patterns where they add or subtract the same number repeatedly. Let them share their patt...

Is square root of 11 an irrational number? How do you know from using a calculator? Thank you. Well, I happen to know that if the square root of a natural number is NOT a whole number, then it is an irrational number. There are no other possibilities. Of course you can't tell by the calculator. The calculator will show you 8 or 10 decimals, but you won't know from that if it's going to continue or not, or if it is periodical or not. But pure mathematics and established, proven theorems will tell you that! : ) A proof that the square root of 2 is irrational Lots of proofs of the same... plus one proving that any root is irrational if it's not a whole number Proof that the square root of any prime is irrational

How do I find the sin or inverse sin of 46 degrees (or any degree) without using a calculator? Thanks. Jackie Finding an "inverse sin" doesn't apply to degrees by the way. We take sine of an angle and get a number; inverse sine is taken from a number and gives back an angle. So is it possible to find values of sine without a calculator? I am sure there are various methods, but these two came to my mind. 1) We can go back to the definition of sine in a right triangle and using a protractor, DRAW a right triangle with that angle. Draw as accurately as you can. Then from the picture again, we need to measure the two sides: the opposite side and the hypotenuse and then calculate their ratio (paper and pencil). Again, measure as accurately as you can. Now, as far as the opposite problem, let's say you know that the sine of some angle is 0.86 or some other number (between -1 and 1). Can we find the angle without the calculator? Draw a right triangle with hyp...

There is controversy over how much elementary school kids should be allowed to use the calculator. Some say it's a no-no altogether, some think it should be used almost all the time - and some think it should be balanced. In my opinion, one should severely restrict the calculator use in early grades - until the student has mastered the basic math facts and can quickly do basic mental calculations. Until then, calculator should be used only for some special projects or illustrations. Why? Because not knowing those facts by heart is a big hindrance when learning fractions, factoring, etc. And because it helps children develop NUMBER SENSE - to be familiar with our number system. Also kids need to learn to do multiplication and long division by hand - it is needed later when those same procedures are used in algebra. Read more at this link: Using calculator in elementary math teaching .