As sal said in the video, sin a = 90-cos a. and cos a = 90-sin a.

angle a has sin 54. what is the cos for that angle? how do you know?

what is cos b? how do you know?

The population of a small rural town in the year 2006 was 2,459. the population can be modeled by the function below, where f(x residents and t is the number of years elapsed since 2006. f(t) = 2,459(0.92)