Unit Circle

Cosine

Picture
On the unit circle, cos = x. it is positive in quad I and IV and is negative in quad II and III.

Problem 1 (easy): Given the coordinates (1/2, √3/2), determine the cosineof that angle.

Problem 2 (medium): Evaluate the trigonometric function cos(8Π/3).


Problem 3 (hard): Use the value of the trigonometric function to evaluate the following functions.
cos t =4/5
cos(Π - t) = ?
cos(t + Π) = ?


Problem 4 (applied): A plane takes off at 25 degrees above the horizontal going 100 mph. how fast would an object moving along the ground have to go to stay directly below the plane?