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Browse High School Euclidean/Plane Geometry
Stars indicate particularly interesting answers or good places to begin browsing.

Selected answers to common questions:
    Classifying quadrilaterals.
    Pythagorean theorem proofs.

Deriving Pi [05/10/2001]

Deriving the Midpoint Formula [08/08/1999]
How is the midpoint formula derived from the distance formula?

Desargues' Theorem [09/22/1999]
What is Desargues' theorem and how can it be proven?

Desargues' Theorem and SSASS [12/15/1998]

Descartes' Square Root Method [10/30/1996]
Why does Rene Decartes' geometric method for finding square roots work?


Determining Equable Shapes [06/15/1999]
Could you please list some equable shapes and show me how you determined them?

Determining Length of Material Remaining on a Roll [11/24/2003]
Is there a mathematical formula to determine the length of material on a roll, given the outside diameter of the core, the outside diameter of the whole roll, and the thickness of the material (determined by a micrometer)?


Diagonals and Tiles [11/17/2001]


Diameter Endpoint [01/26/2003]

Dimensions [08/30/2001]

Distance between Points of Tangency [02/16/2003]
Two circles, one of radius 5, the other of radius 8, intersect at exactly one point, and the center of each circle lies outside the other circle. A line is externally tangent to both circles. Find the distance between the two points of tangency.

Distance From a Point to a Line [09/16/1998]
Derive an equation to give the distance from any point on a 2D plane to a line.

Distance from a Point to a Line [08/20/1999]
Can you show me a straightforward way to derive the formula for the distance from a point to a line: abs(Ax+By+C)/sqrt(A^2+B^2)=D?

Distance from Point to Ellipse [05/19/1997]

Dividing a Circle into 8 Equal Parts [08/19/2002]
If you have a diameter of 14 ft., can you mark off the 1/8 sides of the circumference so that they are equal?

Dividing a Line Segment [03/08/2001]
How do I divide a line segment into a 2:3 ratio using the angle bisector?



Drawing a Locus of Points [05/30/2008]

Eleven Nets of a Cube [11/15/2001]

Enlarging the Penguin Pond [06/03/1999]

Equable Polygons and the Area of a Circle [10/30/2001]
I have found a general formula to work out the side length a polygon (of any shape) must have to be equable, which is closely linked to finding an equation for the area of a circle without using pi (and therefore proving pi)...

Equable Polygons [10/29/2001]


Euclid's Fifth Postulate [6/24/1996]
I am interested in finding some theorems, axioms, or postulates similar to Euclid's Fifth Postulate.

Euclid's Parallel Postulate [2/14/1995]

Euler's Formula [11/26/2001]

Fabric Left on a Roll [03/15/2001]
I am going to write a program for my TI-83+ to calculate how many feet of material are left on a roll.

Figure Not Drawn to Scale [08/16/2003]
A line l is drawn with points A,B,C,D,E, and F, in that order. The points appear equidistant, the figure is not drawn to scale. If AD=BE, which of the following must be true?


Figuring Out Formulas for Area [08/24/1999]

Filling a Garden with Topsoil [2/5/1996]

Find Angle DEA and Angle ADB [4/28/1995]
Given that line AB is parallel to line DC, measure of arc CB=62, measure of angle DAB=104. Find the measure of angle DEA and the measure of angle ADB, and WHY.



Finding Areas of Different Polygons [09/02/1997]

Finding Captain Kidd's Treasure [05/17/2000]
How can you find Captain Kidd's treasure if you can't find the tree referenced in the instructions?


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