Remember that
Coterminal angles are angles in standard position (angles with the initial side on the positive x -axis) that have a common terminal side.
so
To find a positive and a negative angle coterminal with a given angle, you can add and subtract 360° if the angle is measured in degrees or 2π if the angle is measured in radians
N 1
we have
13π/4
subtract 2π
(13π/4)-2π=9π/4
The answer to Part 1 is 9π/4 radians
N 2
we have 10.2 radians
so
10.2 -2π=10.20-6.28=3.92 radians
The answer to part 2 is 3.92 radians
N 3
we have
-189π/20 radians
subtract 2π radians
-189π/20-2-189π/20-2π=-229π/20 radians
The answer to part 3 is -229π/20 radians
