Geometry Expressions NewsletterThe content in this preview is based on the last saved version of your email  any changes made to your email that have not been saved will not be shown in this preview.

Geometry Expressions Newsletter 
April 2012 

NCTM

Three of our authors are giving presentations involving Geometry Expressions at this year's NCTM annual convention in Philadelphia.
 Crop Circle Algebra: Students Teaching Farmers? Larry Ottman Friday April 27th, 11:0012:00, rm 123
 Teaching Proofs to a Digital Generation Irina Lyublinskaya Friday April 27th, 2:003:00, rm 120C
 From Pedal Triangles to Savonius Wind Turbines: Students' Mathematical Modeling Projects Philip Todd Saturday April 28th, 11:0012:00, rm 103A
Or come by our booth: Saltire Software ~ Booth 303.


How to...generate computer code with Geometry Expressions

You can use Geometry Expressions to create computer code in any of the following languages:
 C / Objective C
 C++
 C#
 Visual Basic (.net)
 VBA
 Java
 JavaScript
Here's a simple example.
Let's imagine you want code for the intersection point between two segments.
 First draw the segments and create a point E at their intersection.
 Next constrain the coordinates of the segments end points.
 Now select point E and Calculate / Coordinates
 If you want code which reuses intermediate variables, then select the output and from the right click menu select Output Properties / Use Intermediate Variables / Yes
 Keeping the output selected, do Edit / Copy As / Source Code / C++
 Paste into your editor.
Here is the code generated for the above example:
void z_0( double x_0 , double x_1 , double x_2 , double x_3 , double y_0 , double y_1 , double y_2 , double y_3 , double &z_0_x_ , double &z_0_y_ ) { double z_0_x; double z_0_y; double d_1; double d_0; double phi_0; d_1=((y_2*x_3*(1.0))+(y_3*x_2)); d_0=((y_0*x_1*(1.0))+(y_1*x_0)); phi_0=(((y_0+(y_1*(1.0)))*((x_2*(1.0))+x_3))+((y_2+(y_3*(1.0)))*((x_0*(1.0))+x_1)*(1.0))); z_0_x=(((((x_0*(1.0))+x_1)*d_1)+((x_2+(x_3*(1.0)))*d_0))*pow(phi_0,(1.0))); z_0_y=((((y_0+(y_1*(1.0)))*d_1*(1.0))+((y_2+(y_3*(1.0)))*d_0))*pow(phi_0,(1.0))); z_0_x_ = z_0_x; z_0_y_ = z_0_y; }

Problem of the Month 
Point A has coordinates (0,1). A family of circles is defined whose centers lie on the x axis, and whose radii are a factor k times the distance between point A and their center.
Using Geometry Expressions (or otherwise), show that the envelope of this family of circles is a hyperbola if k<1 and an ellipse if k>1
Show that, in either case, A is a focus of the conic.
(See Salmon's "Higher Plane Curves", article 117)




Electronic Book Bundle
 10 Geometry Expressions eBooks are now available as a bundle for the recessionfriendly price of $79.95 Bundle includes:
 The Tortoise and Achilles
 Calculus Explorations
 The Farmer and the Mathematician
 Developing Geometry Proofs
 101 Symbolic Geometry Examples
 101 Conic Sections Examples
 Using Symbolic Geometry to Teach Secondary School Mathematics
 Connecting Algebra and Geometry through Technology
 Function Transformations
 Exploring with Geometry Expressions
Learning Calculus with Geometry Expressions is a unique electronic resource containing lectureready slides and labready Geometry Expressions files. Available for $6.99 per chapter, or $34.95 for the whole book.


Videos

See our YouTube channel for videos exploring features in Geometry Expressions.
Phil Todd's TechIgnite talk connects central pivot irrigation in Texas to Malfatti's Problem





