Notes 6-1: Radian Measure Radian: The length of the corresponding arc on a unit circle. Arc: A “piece” of the circumference. Sector: A portion or “slice” of a circle. The arc length of the sector is the radian measure of θ.
C = 2πr (or C=πd) since r = 1 C = 2π(1) C = 2π Circumference: unit circle: radius = 1 1 full circle = 360° = 2π radians so…180° = π radians
Summary:
Finding the length of an arc on any circle. s = arc length r = radius θ = central angle in radians If the angle is given in degrees, then convert to radians before calculating the arc length.
p.348 5. Change 240° to radians.
9. Evaluate each expression without a calculator 9. Evaluate each expression without a calculator. (In other words, draw a unit circle and find the exact value.) *See next page for final solutions…
9. Now answer the given expressions (including part b and c)
Given the measurement of a central angle, find the length of its intercepted arc in a circle of radius 15 inches. Round to the nearest tenth. Reminder: s = rθ