MPM2D1-01 Finding altitudes 2016-10-05

We wrapped up your area work (on the chart paper), and then learned to find an altitude given the coordinates of the vertices of a triangle.

If you have triangle $ABC$ with base $AB$, the altitude from $C$ can be found using the following steps:

• Find the slope of $AB$
• Find the slope of the altitude (negative reciprocal of the slope of $AB$ since it’s perpendicular)
• Find the equation of the line through $AB$
• Find the equation of the altitude line

In the example we did today we also found the point $D$ which was the intersection of the altitude with the base. For that we needed to solve the system of equations for those two lines.