Mr. Ohashi's Math 8 Website

Eighth Grade Math at Eckstein Middle School

Tag Archives: interior angles

Friday, 6/2: Angle Relationships (Day 5 of 14)

Learning Target: Use angle relationships to identify angle measures.
Handouts: More with Angle Relationships (Turn in: Mon, 6/5)

We started today by writing down the rule for triangle similarity. We know that if two angles of one triangle match two angles of another triangle, then the third angles must also match and the two triangles must be similar!

Yesterday, we looked at the pattern of angles formed when parallel lines are intersected by another line. There are names for each of these angle relationships! Today, we completed the back page of our notes that have all of the angle relationships in pictures!

If you’d like to see a video describing these relationships, check it out here:

We also had some problems where a triangle was intersected by a line that was parallel to one of its sides. We found that this always creates a similar smaller triangle!

In class, you had to complete #1-6. There is no additional homework, so have a great weekend!

Thursday, 6/1: Parallel Lines and Angles (Day 4 of 14)

Learning Target: Explore parallel lines in order to discover more angle relationships.
Handouts: Angles & Parallel Lines (Turn in: Fri, 6/2)

Today we learned some more angle relationships. When two lines intersect, the angles across from each are equal. Those angles are called vertical angles.

We also looked at the angles that are formed when parallel lines are intersected by another line (a transversal). This forms eight angles with a pattern. The first group of four angles is exactly the same as the second group of four angles!

We wrote the following down in our notes:

If you want to see those patterns visually, check out the video…

In class, you should have finished at least #1-7. There is no additional homework!

Wednesday, 5/31: Triangle Similarity (Day 3 of 14)

Learning Target: Work with triangles in order to explore their angle relationships.
Handouts: Triangle Similarity (Turn in: Thurs, 6/1)

Today we worked with similar polygons. Remember, similar polygons have the same shape but are different sizes – like when we drew dilations in our last unit! You already know that if you have two similar triangles, you can use the scale factor to find the unknown side lengths. Today though, we worked with similar triangles and our focus was on their interior angles.

My demonstration in class showed you that when you enlarge or shrink a triangle, even though the side lengths changes, the angles all stay the same! So if each of the angles in one triangle have the same measure as each of the angles in another triangle, then the two triangles are similar. We don’t even need to look at the lengths of the sides!

As you worked through the classwork, you found a shortcut with the angles on #2. You found that if a pair of triangles have two angle measures in common, then the third angles must be equal too! Therefore, when you have a pair of triangles with two sets of equal angles, then the two triangles are similar!

Your homework is to make sure you have #1-7 complete.

Tuesday, 5/30: Triangles and Angles (Day 2 of 14)

Learning Target: Work with triangles in order to explore their angle relationships.
Handouts: Triangles and Their Angles (Turn in: Wed, 5/31)

Today we looked at angles in triangles. We started by taking down some notes:

We know that the interior angles of a triangle always add up to 180 degrees. So if we know the measures of two of the angles, we can always find the measure of the third!

Finding the measures of exterior angles requires just a little more thought. The exterior angle and the angle next to it will always form a straight line, so the two angle measures must add up to 180 degrees. Then if we know the measure of one of the two angles, we can find the measure of the other.

Your homework is to finish #1-6.