A pendulum has a mass of 3.6 kg, a length of 2.1 meters, and swings through a (half)arc of 26.2 degrees. What is its amplitude to the nearest centimeter?

Answer 1

If by "amplitude" you mean the horizontal back-and-forth motion, that is L*sin26.2 = 0.927 meters = 93 cm (rounded).
There is also up-and-down motion of L*(1 - cos26.2) = 0.216 meters

The amplitude could also be expressed as the half angle, 26.2 degrees. It all depends upon how you define it.