Complementary and Supplementary Angles

Today we looked at complementary and supplementary angles. Complementary angles are angles which add up to 90 degrees. Supplementary angles are angles which add up to 180 degrees. We can use what we know about these angles, as well as look at their adjacent angles, to determine missing angle measurements.

Types of Triangles

Today we learned about different types of triangles - right, acute, and obtuse. We discussed that all triangles have two acute angles. The third angle is what determines its type. If the third angle is also acute, it's an acute triangle. If the third angle is right, it's a right triangle. If the third angle is obtuse, it's an obtuse triangle.

Naming and Measuring Angles

We began the week naming angles. Most of the students were familiar with the types of angles, but we reviewed the important characteristics of straight angles, obtuse angles, acute angles, and right angles.

Next we worked on measuring angles. Measurement is still a very abstract idea for 4th graders, so we began by discussing measurement as a whole. What do we use different measurement tools to measure? I posed the question, "Would a ruler work when trying to measure angles?" In the beginning of our discussion, many kids believed it would. After trying it out, they came to the conclusion that we needed something that measures in degrees. They understood the unit wasn't correct, but weren't sure what degrees actually are, though we had discussed degrees when classifying angles as right, acute, obtuse, and straight.

We went back to everything we already know about angles. Going in a complete circle means we have gone 360 degrees, while only going halfway around means we have gone 180 degrees. We already know that a right angle is 90 degrees. We already know a straight angle is 180 degrees. We know an acute angle measures between 1 degree and 89 degrees. We know an obtuse angle measures between 91 and 179 degrees. Once we illustrated that, we decided we could half each 90 degree piece and figure out where 45 degrees and 135 degrees are located. Next we moved to

Lines and Angles

We began lines and angles this week. We began with introductions of the different types of lines and angles, then moved to making them on dot paper. We moved on to looking at specific lines and angles within a large collection. This lead to the discussion of why it is important to have points on our lines - so we can name the ones we're specifically trying to reference.