Monthly Archives: September 2011

Finding the Equation of a Line Through a Point and Perpendicular to a Line

Find the equation of a line through the point (5,-2) and perpendicular to the line 2x + 5y = 7

In the video at the end I changed all of my signs by multiplying both sides of the equation by -1.  The signs can’t just magically change.

Orienteering – Where am I? Find My Location in Southwest Nebraska

Watch the video and then using the piece of the sectional Jepsen Aviation map for southwest Nebraska find my approximate location on the map using the coordinates I give you in the video.  I am using a very imprecise tool, so do not expect perfection.

Graphing a Quadratic Equation Old School

Some traditional instruction on graphing the quadratic formula.  Here is the cookbook approach. Going to be at a conference today, so here is the concept my Algebra III class is on right now. I Apologize for the poor sound quality.  I did this video using the smart board recorder.  Lots of static.  It could be that my mic was turn off as well.

Find the Distance Between Two Water Towers – Orienteering

In this case I have not actually tried out my measurements in the video to see if they are even close to the actual answer, because when I do this problem the students take their own measurements with their smartphones.   That includes headings and distances.   There are some real rough estimates here, but some great mathematics.   This video is just an example of the set up.  I take my students on a bus out in the country to do this problem.  I split them into groups of 2 or 3, and told them that whomever can prove their answer the closest with the measurements they collect will be the orienteering champions.  Since roads all follow north, south, east, west lines.  It is easy to take heading measurement in one location to two distant objects.  Drive East a certain distance get out and take the measurements again.  For instance in the image  below we took 6 measurements.  The headings to each tack at each endpoint of the red and blue lines.

The red and blue line segments are exactly one mile. We took headings at each endpoint and created two problems. With these measurements it is possible to find the distance between the two thumb tacks.