MA.912.G.6.1Determine the center of a given circle. Given three points not on a line, construct the circle that passes through them. Construct tangents to circles. Circumscribe and inscribe circles about and within triangles and regular polygons.
MA.912.G.6.2 Define and identify: circumference, radius, diameter, arc, arc length, chord, secant, tangent and concentric circles.
Also addresses MA.912.G.6.5.NGSSS
CROP CIRCLES A series of crop circles was discovered in Alberta, Canada, on September 4, 1999. The largest of the three circles had a radius of 30 feet. Find its circumference.
Since the radius is 30 feet, and d = 2r, the diameter = 2(30) or 60 feet.
C = dCircumference formula
= (60) Substitution
= 60 Simplify.
≈ 188.50 Use a calculator.
Answer: The circumference of the crop circle is 60 feet or about 188.50 feet.Example 4