Tag Archives: computers

“Pupils learn poorly when using most computer programs”

.The future: I\(I love this cartoon)

Politics 0448
.Here are two posts worth a read, showing the rheeformed way forward, and consequences

reading-between-the-lines:Obamas-testing-action-plan/
sciencedaily.com/computers_math

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Filed under competency based, education, future

Rigid motions are actually useful !

I am currently reconstructing my geometrical construction application, Geostruct, to run in a web page using javascript.

One of the actions is to find the points of intersection of a straight line with a circle. Here is a gif showing the result:

gif line and circle

The algebra needed to solve the two simultaneous equations is straightforward, but a pain in the butt to get right and code up, so I thought “Why not solve the equations for the very simple case of the circle centered at the origin and the line vertical, at the same distance (a) from the centre of the circle

line vertical circle at origin

Then it is a simple matter of  rotating the two points (a,b) and (a,-b) about the origin, through the angle made by the original line to the vertical, and then translating the circle back to its original position, the translated points are then the desired points of intersection.

The same routine can be used for the intersection of two circles, with a little bit of prior calculation.

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Filed under geometry, math