Archive | Coordinate Plane

Reader Input on Slope Post

A longtime reader of Turtle Talk, Jeff LeMieux, of Oak Harbor, WA, sent in a suggestion based on my post yesterday about positive and negative slope. Jeff found a way to help students remember not only positive and negative slope, but also the infinite slope of vertical lines, and the 0 slope of horizontal lines [...]

Helping Students REMEMBER the Difference in ‘LOOK’ Between Positive and Negative Slope

Some ideas just slap you in the face. I got slapped this morning as I was flying home from LA to Albuquerque. Those little cocktail napkins they hand out with “beverage service” often give me the urge to write. So this morning, nerdily enough, as I sipped my orange juice at 30,000 feet above the [...]

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Origins of the Coordinate Plane

One of the legends of math relates to the invention of the coordinate plane system. The legend states that Descartes was inspired to invent this system after watching a fly move around on the ceiling over his bed. This post tells the story and points out its relevance for modern math teachers.

Not all variables are created equal

Variables do not all serve the same purpose. Making this clear helps students more deeply understand algebraic equations, such as the equation for a line. This post shows how to understand the two kinds of variables in the slope-intercept form of a linear equation.