Find the radian measure of the angle: a) 20 °; b) 80 °; c) 120 °

Let’s use the formula for converting degrees to radians:

α [rad] = a [°] * π / 180 °,

where a [°] is the degree measure of the angle, α [rad] is the radian measure of the angle.

a) Find the radian measure of the angle equal to 20 °:

α [rad] = 20 ° * π / 180 ° = (20 ° * π) / 180 ° = (reduce the fraction by 20 °) = π / 9.

b) Find the radian measure of the angle equal to 80 °:

α [rad] = 80 ° * π / 180 ° = (80 ° * π) / 180 ° = (reduce the fraction by 20 °) = (4 * π) / 9.

c) Find the radian measure of the angle equal to 120 °:

α [rad] = 120 ° * π / 180 ° = (120 ° * π) / 180 ° = (reduce the fraction by 60 °) = (2 * π) / 3.

Answer: a) 20 ° = π / 9; b) 80 ° = (4 * π) / 9; c) 120 ° = (2 * π) / 3.