Curated OER
Circles: Geometry Review Worksheet
Tenth graders solve and complete 14 different geometry problems. First, they find the area and circumference of a circle with a given radius. Then, they find the area between a circle and an inscribed equilateral triangle given the...
Curated OER
Radian Measure
Young mathematicians identify central angles, arcs and radius of circles in this pre-calculus lesson. They identify the proportion of the circle based on its radius while they convert between degrees and radians measurements.
Curated OER
Arc Length and Sectors
Find the length of an arc. High schoolers relate central angles to the area and length of a sector and graph circles on the TI to make predictions.
Curated OER
Reference Angles
Learn how to measure the reference angles in degrees and radians. High schoolers find reference angles that are coterminal with a given angle.
Texas Instruments
Area of Circles
High schoolers explore circles. In this algebra/geometry lesson, students discover the formula for the area of a circle, as they investigate the ratio of the area of a circle to the radius^2.
AAA Math
Aaa Math: Circumference of a Circle
Calculating the circumference or perimeter of a circle has gotten easier with this formula and practice for finding the circumference.
Maths Challenge
Maths challenge.net: Semi Circle Lunes
A lune of a circle is defined and a problem of finding the area of two lunes is given.
Cuemath
Cuemath: Area of a Circle
This mini-lesson explores the area of a circle. Provides a definition, examples, and practice questions with answers.
Cuemath
Cuemath: Arc Length
Learn all about arc length. This lesson targets what is arc length and the different formulas used to calculate it. Check-out the interactive simulations to know more about the lesson and try your hand at solving a few interesting...
Cuemath
Cuemath: Central Angle
Learn all about the basic properties of central angles. This lesson targets what is a central angle, central angle formula, central angle calculator, theorem of central angle, how to find central angles, and how to apply them while...
Math2
Math2: Circles
This site has many useful formulas and examples relating to circles, including related definitions, circumference of a circle, area of a circle, length of a circular arc, area of a circular sector, equation of a circle in cartesian...
National Council of Teachers of Mathematics
The Math Forum: Elementary Geometry Circles
The Math Forum offers an archive of question and answer sessions on circles and how they relate to geometry.
University of Georgia
University of Georgia: Arcs, Central Angles, Arc Length & Sector Area
This site provides practice problems for calculating central angles and calculating arc length.
Texas Instruments
Texas Instruments: Relation Between Central Angle and Inscribed Angle Measure
Students investigate the relationship between measure of central and inscribed angles in a circle.
Texas Instruments
Texas Instruments: Relationship of Angles to the Circle
In this activity, students recognize the relationship of angles to circles. They study the Inscribed Angle Theorem and its corollaries.
Texas Instruments
Texas Instruments: Arc Length and Area of Sectors
This is an introduction to finding the arc length and area of sectors of circles. Students should have the formulas for Circumference and Area of circles.
Texas Instruments
Texas Instruments: Central Versus Inscribed Angles in Circles
Using Cabri Jr. to explore the connection between central and inscribed angles along with their arc measure.
Texas Instruments
Texas Instruments: Angles Formed by Intersecting Chords, Secants, and Tangents
In this activity, students will investigate properties of angles and arcs formed when chords, secants, and tangents intersect and intercept arcs in a circle. They discover several important theorems concerning circles and arc sizes. They...
Texas Instruments
Texas Instruments: Cabri Jr. Inscribed and Central Angles
This activity uses Cabri Jr. to explore the relationship between inscribed and central angles subtended from the same arc of a circle.
Texas Instruments
Texas Instruments: Cabri Jr. Inscribed Angles
This activity uses Cabri Jr to discover that inscribed angles subtended by the same arc in a circle are congruent.
Texas Instruments
Texas Instruments: Arcs and Angles: Explore Inscribed & Central Angle Properties
This activitie uses the power of Cabri Jr. to explore the relationship between inscribed angles and central anlges in cirles.
Texas Instruments
Texas Instruments: Relationship Between Radius and Tangent to a Circle
Generalize that a tangent and a radius form a 90-degree angle.
Texas Instruments
Texas Instruments: Approximation of Pi Using an Area Model
Students will approximate pi by setting up trigonometric ratios and calculating the areas of regular polygons inscribed within and circumscribed about a circle.
Texas Instruments
Texas Instruments: Inscribed Angles Intercepting the Same Arc
Students investigate the properties of angles inscribed in a circle. They use the drawing and measurement tools of Cabri Jr. to draw and measure certain angles, and establish the relationship between angles that intercept the same arc.