Illustrative Mathematics
Sum of Angles in a Polygon
How can learners use algebra to solve a geometry problem? Help learners create an equation that shows the relationship between the number of sides of a polygon and the sum of the interior angles. Students are asked to divide the...
Illustrative Mathematics
Find the Missing Angle
This one activity requires young geometers to pull together information they are currently learning with things they have learned previously. Here they rely on understanding something about parallel lines, alternative interior angles,...
EngageNY
More on the Angles of a Triangle
Angles and triangles: they're all connected. Uncover the connections between angles in triangles. Scholars learn how to find both exterior and interior angle measures in triangles. The instructional activity emphasizes the vocabulary...
Curated OER
Interior Angles of Regular Polygons
Students investigate the interior angles of a triangle. In this geometry lesson, students create the formula to calculate the angles inside a triangle. They observe the total sum of a triangles angle on the navigator.
EngageNY
Solve for Unknown Angles—Angles in a Triangle
Assist your class with each angle of geometry as they use exterior angles to form linear pairs with adjacent interior angles. They cover multiple vocabulary terms and work practice problems, complete with justifications, before...
Curated OER
Triangles: Triangle Inequalities
Using SketchPad on their calculators to construct triangles, students measure exterior angles and remote interior angles of their constructed triangle. Students develop the triangle inequality from observation and exploration with their...
Mathematics Assessment Project
Applying Angle Theorems
Polygon ... an empty bird cage? After finding the angles of a polygon, young mathematicians use the provided methods to solve the problem in multiple ways.
Radford University
How Much is in There? A Polygon Investigation
Try to find the triangles in various polygons. An investigation has learners develop a formula for the sum of the measures of the interior angles of a polygon. They use manipulatives to partition each polygon into triangles, then...
Curated OER
Angles of a Triangle
Learners explore the measures of the angles of a triangle in this geometry lesson. They use Cabri Jr. to investigate the sum of the measures of the interior angles of a triangle, and examine the relationships between the interior and...
Curated OER
Measuring Angles in a Triangle
High schoolers investigate the sum of the measures of the angles of a triangle. They draw a triangle and measure the interior angles. Using Cabri Jr., learners find the sum of the measures of the interior angles. The lesson provides an...
Curated OER
Midsegments of a Triangle
High schoolers analyze midsegments of triangles in this instructional activity. They use Cabri Jr. software to observe the relationships between interior angles and midsegments of triangles. Specific instructions for creating this...
Curated OER
Triangle Classificaition with Geometer's Sketchpad.
Learners use Geometer's Sketchpad to draw triangles and explore the classificaiton of each using the mearsures of interior angles and the lengths of the sides.
EngageNY
Angle Sum of a Triangle
Prove the Angle Sum Theorem of a triangle using parallel line and transversal angle relationships. Pupils create a triangle from parallel lines and transversals. They find angle measures to show that the angles of a triangle must total...
EngageNY
Unknown Angle Proofs—Proofs of Known Facts
Lead the class in a Greek history lesson with a geometric twist. Pupils relate a short video about geometric properties to modern-day methods of solving for unknown angles. They discuss parallel line theorems and complete...
Curated OER
The Sum of All Angles
Students add up the different angles using the angle addition postulate. In this geometry lesson, students differentiate between interior and exterior angles. They calculate the different angles for triangles and use proof to show their...
Curated OER
Angle-Side Relationships
Students calculate the different sides and angles of a triangle. In this geometry lesson, students use triangular properties to define the relationship between two triangle. They identify missing angles using the interior angle theorem.
Curated OER
Triangle Inequality Theorem
Students use the inequality theorem to solve triangles and their properties. In this geometry lesson, students are given spaghetti of different lengths and asked to create triangles. They conclude the necessary length needed to make a...
Curated OER
Geometric Properties
Young scholars find triangular angles using the angle theorem. In this geometry lesson, students describe labeled triangles, use the pythagorean theorem, and rewrite information about triangles in standard form.
Curated OER
Does Your Field Measure Up
Young scholars measure angles using a plane table kit. In this geometry lesson, students use trigonometric identities to find the values of the length of a football field.
Curated OER
Altitude, Median, and Angle Bisector of a Triangle
Learners investigate the special properties of an altitude, a median, and an angle bisector and explore how these special segments divide the area of a triangle. The dynamic nature of Cabri Jr. allows pupils to form and verify conjectures.
Curated OER
Sum of Interior/Exterior Angles with Wilbur
Young scholars identify the interior and exterior measures of polygons. In this geometry lesson, students identify the formula for interior angles of polygons. They differentiate between triangular and polygons angles.
Curated OER
Triangle Congruence
Students use web applet to create congruent triangles. In this geometry lesson, students differentiate between congruent and similar. They create shapes online and drag those shapes around to create visuals of triangles.
Curated OER
Obtuse Triangles
Fourth graders explore obtuse triangles. In this geometry instructional activity, 4th graders make obtuse triangles with paper and scissors. They determine how to find the center of their triangle.
Radford University
Parallel Lines Cut by a Transversal
Use the parallel lines to find your way. After first reviewing geometric constructions and the relationships between angles formed by parallel lines and a transversal, young mathematicians write proofs for theorems relating to parallel...