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Mathigon
Mathigon: Geometry: Circle and Pi: Degrees and Radians
Rather than dividing a circle into some number of segments (like 360 degrees), mathematicians often prefer to measure angles using the circumference of a unit circle - a circle with radius 1. This way of measuring angles is called...
Khan Academy
Khan Academy: Points Inside/outside/on a Circle
Given the center and radius of a circle, determine if a point is inside of the circle, on the circle, or outside of the circle.
Illustrative Mathematics
Illustrative Mathematics: G Co Seven Circles Ii
In this task, seven pennies are placed in a circle so that they are all touching one in the center and their neighbors. Students are asked to find as many rigid motions of the plane as they can which are symmetries of this configuration...
Illustrative Mathematics
Illustrative Mathematics: G Gpe, F Tf Coordinates of Points on a Circle
For this task, students are shown a unit circle in a plane and an angle measured from the x-axis. They must determine the coordinates of the line segment for the angle and answer a question about the sum of the coordinates. The purpose...