Angles Upon Angles

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SWBAT construct angle bisectors and identify angle relationships.

Big Idea

Angles pair up with special names in this lesson featuring a brain pop and pair-share investigations which are geared for differentiation instruction.

Do Now, Pair-Share and Construction

35 minutes

Do Now:

-Students will be asked to find a missing angle given an acute angle on a straight line.  This Do Now is a great opportunity for teachers to review key terms relating to angles like acute, obtuse, right and straight angles.  This Do Now also asks students to apply their knowledge of straight angles measuring 180 degrees, which is a great preview for introducing supplementary angles later in the lesson.   

Pair-Share Review:

Students can answer the review questions that focus on the video, and also on students’ understanding of angle bisectors and application questions. Students can work in pairs on this and then you can review with students as a whole class or ask students to write their work on the board to review.  These questions about angle bisectors helps students to transition into the construction of angle bisectors.


Constructing an Angle Bisector:

In student notes, steps for constructing an angle bisector are provided as well as a link to a video demonstrating this construction.  I have provided one example for students to try, after watching a demonstration.  To differentiate this part of the lesson, teachers may want to ask student to first watch a demonstration of constructing an angle bisector, and then try with a partner, and then try on their own after drawing their own angle.  The video is a great resource for students who are absent.


After constructing the angle bisector, a thinking question helps students to think about why this construction works.  Although students have not learned about congruent triangles yet, the drawing in student notes, shows many different shapes and students can take this opportunity to think about what shapes are created when an angle is bisected and how these shapes are related.  

Notes and Review

25 minutes

Practice, Homework and Exit Ticket

10 minutes

Practice:  There are three practice examples that teachers can lead students through to practice applying the concepts learned in class today.  Example 1 is particularly important because it asks students to use algebra to find measures of complementary angles without a picture.  You should stress that drawing a picture helps everyone to visualize information provided, and being asked.      

Activity/Homework:  Students will be asked to finish activity in class, and any questions that are not finished will become homework. You may also want to ask students to work on creating flashcards of key vocabulary learned in today’s class.   


Exit Ticket:  Students will complete an exit ticket question that students to represent the complement and supplement of an angle given a measurement and an expression.  This is another great connection to algebra and vocab for this day’s lesson.