Solve for θ by using the formula ω = θ/t:

ω = 5π/4 radians per sec, t = 8 sec

Solve for ω by using the formula v = rω:

v = 17 m per sec, r = 9 m

A gear underneath the moving walkway at an airport in Amsterdam rotates at 230 revolutions per minute. Calculate its angular speed in radians per second and express the answer to the nearest tenth.

Without using a calculator, determine the value of the following trigonometric expression:

[sin (π/21)] ² + [cos (π/21)] ²