Skip to main content
Logo image

Section 6.1 Degree and Radian Measure (TR1)

Subsection 6.1.1 Activities

Definition 6.1.1.

An angle is formed by joining two rays at their starting points. The point where they are joined is called the vertex of the angle. The measure of an angle is the amount of a circle between the two rays.

Activity 6.1.2.

We know that if you complete a full turn of the circle the angle created will be 360 degrees. Use this to estimate the measure of the given angles.
(a)
  1. 45
  2. 90
  3. 135
  4. 180
Answer.
B
(b)
  1. 45
  2. 90
  3. 135
  4. 180
Answer.
D
(c)
  1. 45
  2. 90
  3. 135
  4. 180
Answer.
C

Definition 6.1.3.

An angle is in standard position if its vertex is located at the origin and its initial side extends along the positive x-axis.
An angle measured counterclockwise from the initial side has a positive measure, while an angle measured clockwise from the initial side has a negative measure.

Activity 6.1.4.

Find the measure of the angles drawn in standard position.
(a)
  1. 45
  2. 90
  3. 135
  4. 180
Answer.
A
(b)
  1. 180
  2. 90
  3. 180
  4. 90
Answer.
C
(c)
  1. 30
  2. 150
  3. 210
  4. 210
Answer.
D
(d)
Draw an angle of measure 225 in standard position.
Answer.

Remark 6.1.5.

Activity or remark - Something about the circumference of a circle being another way to measure the angle. C=2πr divide both sides by the radius, so a full circle or 360=2π radians

Definition 6.1.6.

One radian is the measure of a central angle of a circle that intersects an arc the same length as the radius.

Activity 6.1.7.

Using the fact that one turn around the circle is 360 and also 2π radians. Find the measure of the following angles in radians.

Activity 6.1.8.

Using the fact that one turn around the circle is 360 and also 2π radians. Find the measure of the following angles in degrees.

Subsection 6.1.2 Exercises