Chapter 2 - Limits - 2.1 The Idea of Limits - 2.1 Exercises - Page 60: 22

Conjecture: the instantaneous velocity at $t=\pi/2$ is $-20$ ft/s.

(The table in the screenshot was set up using the calculator at desmos.com). The average velocity appears to approach $-20$ as the time interval gets shorter. Conjecture: the instantaneous velocity at $t=\pi/2$ is $-20$ ft/s.