Illustrative Mathematics
Finding an Unknown Angle
Teach your class how to apply their knowledge of geometry as they explore the unknown. In order to find an unknown angle, students must understand that rectangles have four interior right angles, that right angles have 90 degrees, and...
Willow Tree
Angle Measurement
What do you create when you rotate a ray? An angle! Teach all the angle basics including naming, measuring, supplements, and complements.
Willow Tree
Angle Sum Property of Triangles
All triangles have some things in common. Using these properties of triangles, learners find missing angle measures. Scholars use the Angle Sum Property and properties of special triangles throughout the lesson.
EngageNY
Solve for Unknown Angles—Angles and Lines at a Point
How do you solve for an unknown angle? In this sixth installment of a 36-part series, young mathematicians use concepts learned in middle school geometry to set up and solve linear equations to find angle measures.
Curated OER
Vertical Angles
With a clean, direct resource like this one, learners can easily focus on the task at hand, which is clearly communicated. They practice figuring the missing measures of vertical angles given the measure of their complement or...
Curated OER
Angle Relationships
Tenth graders explore the angle relationships that exist when two lines intersect. In this geometry lesson, 10th graders estimate the measure of given angles and use their graphing calculator tools. Students use this knowledge to find...
EngageNY
One-Step Problems in the Real World
Mirror, mirror on the wall, which is the fairest resource of them all? Individuals write and solve one-step equations for problems about angle measurement, including those involving mirrors. Both mathematical and real-world problems are...
EngageNY
The Inscribed Angle Alternate – A Tangent Angle
You know the Inscribed Angle Theorem and you know about tangent lines; now let's consider them together! Learners first explore angle measures when one of the rays of the angle is a tangent to a circle. They then apply their newfound...
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 lesson emphasizes the vocabulary related to these...
Curated OER
Know Your Angles
Explore types of angles and the characteristics of each. After observing a PowerPoint Presentation, learners tour the school facilities and use a digital camera to capture prescribed angles. Using the digital pictures and written...
Curated OER
Supplementary, Complementary, and Vertical Angles
By using circles that they cut out and label themselves, learners literally "get a grip" on the angles they identify: supplementary, complementary, and vertical. They solve missing measurements based on properties of supplementary,...
EngageNY
Similarity and the Angle Bisector Theorem
Identifying and verifying reproducible patterns in mathematics is an essential skill. Mathematicians identify the relationship of sides when an angle is bisected in a triangle. Once the pupils determine the relationship, they prove it to...
EngageNY
Unknown Angle Proofs—Proofs with Constructions
Provide your emerging mathematicians with the tools to learn as they incorporate auxiliary lines to solve unknown angle proofs in this continuing segment. They decipher information from a diagram to uncover the missing pieces and...
EngageNY
Unknown Angle Problems with Inscribed Angles in Circles
We know theorems about circles—now what? Class members prove a theorem, with half the class taking the case where a point is inside the circle and half the class taking the case where a point is outside the circle. The lesson then...
Curated OER
Hypatia: Angles
Introduce your young geometers to Hypatia, the first noted Greek female mathematician, and the properties of angles. Though this resource is missing worksheets that are needed to complete the lesson, the structure is sound and learning...
EngageNY
Unknown Angles
How do you solve an equation like trigonometry? Learners apply their understanding of trigonometric ratios to find unknown angles in right triangles. They learn the meaning of arcsine, arccosine, and arctangent. Problems include basic...
Messenger Education
My Angle on Cooling—Effect of Distance and Inclination
When exploring Mars, spacecrafts are exposed to 5-11 times more sunlight than when near Earth. Groups of pupils complete a hands-on activity to explore how distance and angle of the sun affect temperature. Through discussions, they then...
Mathematics Assessment Project
Identifying Similar Triangles
Math whizzes work with angle sums and exterior angles to figure out the measure of other angles. This particular publication provides comprehensive support in the form of an anticipatory activity, questions designed to prompt discussion,...
Curated OER
Geometry: Lesson 8
Eighth graders engage in a lesson that is concerned with the finding of angles that are found in different two dimensional figures. They compare and contrast exterior and interior angles while also determining the unknown measures of...
Curated OER
Exploring Angle/Pair Relationships
Learners find missing angles and sides of triangles. In this geometry lesson, students create intersecting lines to measure angles. They use Cabri Software to create virtual angles.
Curated OER
Indirect Measurement with Similar Triangles
Students use similar triangles to find missing heights. In this using similar triangles to find missing heights lesson, students use proportions to find the heights of missing side lengths. Students find the height of trees and...
Curated OER
Angles That Pair
Students identify angles. In this angles that pair lesson, students identify adjacent, vertical, complementary, and supplementary angles. They use straws, pretzel sticks to demonstrate given types of angles.
Curated OER
Angles
Students measure angles using a protractor. In this geometry lesson, students solve for the missing angles using equations set to the theorem of triangles. They measure missing angles through construction and identify congruent angles.
EngageNY
More About Similar Triangles
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...