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4.1 Angle Measure. y. x. Standard Position : an angle drawn in the xy-plane w/ the vertex at the origin and the initial side on the positive x-axis. Counterclockwise = Positive Angle Clockwise = Negative Angle. To convert… degrees to radians, multiply by:
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y x Standard Position: an angle drawn in the xy-plane w/ the vertex at the origin and the initial side on the positive x-axis.
Counterclockwise= Positive Angle • Clockwise= Negative Angle
To convert… • degrees to radians, multiply by: • radians to degrees, multiply by:
Coterminal Angles: 2 angles who have the same terminal sides. • To find positive or negative coterminal angles: Add or Subtract 360 or 2.
Ex 3: Find 1 positive & 1 negative angle that are coterminal with the angle: a) b)
Length of a Circular Arc: • s = arc length • r = radius • = angle measure (rad)
Area of a Circular Sector: • A = sector area • r = radius • = angle measure (rad)
Ex 5: Find the length of an arc that subtends a central angle of 45 in a circle of radius 10 m.
Ex 6: A sector of a circle of radius 24 mi has an area of 288 mi2. Find the central angle of the sector.
B 1 C A 1 • Radian: If a circle of radius 1 is drawn w/ the vertex of an angle at its center, then the measure of the angle in Radians (rad) is the length of the arc that subtends the angle. mBAC = length of Arc BC Circumference = 2