Using Data from Graphs: Interpolation Vs. Extrapolation

[caption id="attachment_28677" align="alignright" width="480"] Fig. 1. Plot of cook time vs. temperature[/caption]A familiar technique used when collecting data is to graph the results. For instance, suppose you want to see how quickly the internal temperature of a roast of pork rises in a 250° F oven. Nine internal meat temperature measurements are taken over a period of an hour-and-a-half, or 180 minutes. Collecting the Data After 20 minutes, the internal temperature of our pork roast is 60° F. Twenty more minutes yields 95° F. At 60 minutes, the temperature is 118° F, whereas the temperature is 139° F after 80 minutes. At 100 minutes, we read 148° F. When two hours have passed, we obtain 156° F. 140 minutes of cooking puts us at 163° F, while 160 minutes gives…

Sphere Reciprocal? Not Inside Out, But Equation Inverse?

One way of mathematically representing a very simple sphere in 3D space is, r2 = x2 + y2 + z2 where r equals a radius of the sphere. Solving in terms of x, y, and z, we get, x = √(r2 — y2 — z2) y = √(r2 — x2 — z2) z = √(r2 — x2 — y2) A Sphere Reciprocal Now a sphere may be the most aesthetically pleasing of the simple geometric curves. So it is natural to wonder, concerning a sphere, what if…? So what if we convert the equation into an equation for a sphere reciprocal? No, not turn the sphere inside out. Rather an inverse of the equation of a sphere? What is the graph of, r2 = 1/( x2 + y2 + z2)…

Point on a Line, a Line on a Plane, and a Plane in Space

Each point has a specific location. Two points determine a line. Three points determine a plane. Let us consider some simple math derivations to arrive at a format for each. For simplicity’s sake, we will use the familiar x, y, z Cartesian coordinate system. We begin with a point on a line. First, Point on a Line In space, a single point has an x value, a y value, and a z value. If the coordinate system chosen for the point is a simple 1-D line, then only one variable – say x – is needed to describe it. Then, since there is no y or z to consider, the mathematical description of the point is x = c But let us, for reasons that will be understood later, write…

Analytic Geometry: The Ellipse and the Circle

The circle is really a special type of ellipse. In analytic geometry, an ellipse is a mathematical equation that, when graphed, resembles an egg. An ellipse has two focal points. The distance apart between the two points is one way of describing a particular ellipse. If the two points come together the ellipses become a circle with the point at its center. The equation for an ellipse is, x2/a2 + y2/b2 = 1 In this equation, "a" and "b" are constants that determine the shape of the ellipse, whereas x and y are variables, i.e., they can take on a host of values. When the value for x is known, the value for y is determined. Or, if it is y that is known, then x is determined. If a…