# Altitudes of Triangles

- Author:
- Mathew Purser

- Topic:
- Triangles

We are going to construct the

**altitudes**of a triangle now. The altitude of a triangle is sometimes called the height of the triangle. Just like when your height is measured, we need to draw the altitudes "vertically" from the opposite side. Now, as you can see in the triangle below, we can easily draw an altitude from C using the perpendicular through a point tool (draw a perpendicular to AB through C). but what might be interesting to learn is that there are two other altitudes in all triangles. If the triangles was rotated and B was where C was, we could draw an altitude through B onto AC and the same for A; draw those altitudes now. If you get stuck, use the video but try to complete this on your own!## Think about it!

What do you notice about these altitudes you drew? If you move A, B, or C around, what changes? What stays the same? Move A,B, or C so that the triangle is acute and describe what you see. Make the triangle right, what do you see? Make the triangle obtuse, what do you see?