Section 6-1

Angles and Radian Measure

Degree/Radian Conversion Formulas

Change 115° to radian measure in terms of π23π/36

Change radians to degree measure.

-157.5°

Evaluate Cos 4π/3

Evaluate tan 5π/4

Circular Arc Central angle

The length of any circular arc s is equal to the product of the measure of the radius of the circle r and the radian measure of the central angle θ that it subtends. s= rθ

sθ

Given a central angle of 125°, find the length of its intercepted arc in a circle of radius 7 centimeters. Round to the nearest tenth.

125°= 125° x π/180° = 25 π/36 or 2.18

s=2.18 x 7= 15.3

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