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Measuring Segments
- Ruler postulate: The points on any line can be paired with real numbers so that, given any two points P and Q on the line, P corresponds to zero, and Q corresponds to a positive number
- If Q is between P and R, then QP + PR = QR
- If PQ + QR = PR, then Q is between P and R
- Pythagorean Theorem: In a right triangle, the sum of the squares of the measures of the legs equals the square of the measure of the hypotenuse
- The distance d between any two points with coordinates (x1, y1) and (x2, y2) is given by the formula

Measuring Segments
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
- Intro
- Segments
- Ruler Postulate
- Segment Addition Postulate
- Segment Addition Postulate
- Pythagorean Theorem
- Pythagorean Theorem, cont.
- Distance Formula
- Extra Example 1: Find Each Measure
- Extra Example 2: Find the Missing Measure
- Extra Example 3: Find the Distance Between the Two Points
- Extra Example 4: Pythagorean Theorem
































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Post by Suneet Dash on May 31, 2011
i must say, great video
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Post by Ahmed Shiran on June 4, 2011
Great work by Mary...
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Post by Pangayar Selvi Shanmugasundaram on August 9, 2011
realy iam telling, its wonderful vedio...
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Post by Giri Iyer on November 10, 2011
Very well done and explained.. I am teaching my son geometry and these lessons are so clear conceptually that even I can recall these concepts now :)
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Post by Joseph Reich on June 20, 2012
For the question: "Write a mathematical sentence given segments ED and EF." E does not have to be in the middle:
in the case:
E-------D------F
the mathematical sentence would be EF - ED = DF
In the case:
E----F-------------D
the mathematical sentence would be ED - EF = DF
Also, in the question, ED and EF should have a bar over them because you are talking about segments and not measures
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Post by Catherine Henderson on July 31, 2012
Wow,
That was great!
1 answer
Sat Mar 2, 2013 1:53 AM
Post by chun yung on November 27, 2012
I have a question on the distance formula, why do they have to make it (x2-x1)+(y2-y1) if u put (x1-x2)+(y1-y2)u could get the same answer.
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Post by Mohammed Abdullah on December 13, 2012
In the video it shows d=square root x1-x2)squared+(x1+x2) squared, in the quick notes they subtract the square roots.
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Post by Edward Hook on February 18 at 03:04:55 PM
Everybody loves your teaching style Mary and I have to say that I do too!
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Post by Kenneth Montfort on February 18 at 04:11:41 PM
Just a quick heads up, your distance formula in your quick notes is incorrect and you might want to include the correlation between the PyT formula and the distance formula, so that it is clear why you are supposed to add the two components instead of the subtraction that you highlight. It super confused at me at first until I looked it up.
1 answer
Last reply by: Manfred Berger
Mon May 27, 2013 11:47 AM
Post by bo young lee on February 19 at 08:00:51 PM
at the educator.com where can i find more about the
pythagorean theorem???
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Post by Manfred Berger on May 27 at 11:37:03 AM
So what the Segment Addition Postulate is saying is basically that colinearity is transitve, isn't it?
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Post by julius mogyorossy on June 3 at 02:19:32 PM
Ms. Pyo, I am probably making a fool out of myself again, ask Dr. Carleen, but what would the absolute value of 2 + -5, be, it seems to me it would be 3, but it seems that mathematicians think it should be 7. I was very interested to learn that quadratic equations lie when they are factored, they lie and tell the truth at the same time. Luckily I don't have to factor or use a test point to see where the solution set is, I can see it when I see the equation(s). I found Algebra 2 very interesting, I can't wait to see what Calculus is all about, I have no clue what Trigonometry is about. I have been blessed with incredible instincts, super human, life over death, they are the reason I am still alive. I think I am going to make an incredible discovery having to do with Geometry, I have always sensed incredible potential in Geometry, I have read that incredible things have been allegedly proven having to do with Geometry, I wonder if it is true. Some day I shall do these experiments myself. The knowledge Dr. Carleen gave to me forced scientists to surrender to me, unofficially, some day, officially. I never thought I would see that day, I thought they would do me like Pasteur. Some day you shall know what I am referring to.
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Post by julius mogyorossy on June 3 at 04:51:02 PM
So the distance formula is just a fancy Pythagorean formula, a distance problem is just a Pythagorean problem in disguise. Am I being redundant in saying this, if so please forgive me, sometimes I say something I think will make people go crazy, and they are bored, other times I say something I think might be boring and humans go crazy, I have trouble understanding how humans think. The Pythagorean formula was one of the very few equations/formulas I knew before I came to Educator.com, I didn't really need to know any of them, but I knew they would make a big deal out of it if they found out I didn't know them, even though they would know I didn't really need to know them, my problem was never with the math, of this one theory, but with the logic of it, the logic of a child, literally. You can't believe the incredibly brilliant, sexy, questionable, things I have said about Algebra, on my blog page, part of my website, that one teacher who was fired, obviously knew who I was, was doing an homage to me. I can't wait to teach Algebra, then it will be legal to teach Algebra that way, I will make it so, spoonful of sugar, as they say. I can't wait to be a college Algebra professor, after I save the world, retire. I am very grateful to Educator.com, I was very happy to see Educator.com advertised on my blog page, against my will, I wonder if my so called free blog page is costing me millions of dollars in lost revenue fees. Educator is really allowing me to show off my super genius. Thanks.