CLASS 9 · LEARNING KNOWLEDGE
Circle and circle parts
How it works
The radius connects the center and the circle line. The diameter is twice as long. The arc and sector area each correspond to the angle's share of the whole circle.
Note
U = 2 π r; A = π r²; Sector A = α / 360° · π r².
U = 2 π r; A = π r²; Sector A = α / 360° · π r².
An example
A circle has radius 9 cm. Calculate the circumference. Use π without intermediate rounding. Round to two decimal places. Give the result in cm.
U = 2 π r = 2 · π · 9. Result: 56.55 cm.
Try it yourself now
50 Exercises · three difficulty levels · selection and number input
To the learning unit →Own explanation and own practice exercises by AmyMath. Subject reference framework: KMK Educational Standards Mathematics ESA/MSA. The topic assignment may vary by federal state.