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Home > A2C > Chapter 13 > Lesson 13.1.2 > Problem 13-32

13-32.

Salina, Tamara, and Uma are working on their homework together. Salina tells her friends that she got  for the inverse cosine problem she is working on and asks if they got the same answer. Tamara says she got , and Uma volunteers her answer of . Is it possible that these are all solutions to the same problem? Justify your answer.

Picture a unit circle. Is it possible for the cosine of three different angles in three different quadrants to be the same?

Use the unit circle below to help you. Is cosine the same for all of these angles?

Unit Circle, with 3 points, connected with dashed segment, perpendicularly to the x axis, as follows, first quadrant, 52 degrees, second quadrant, 128 degrees, fourth quadrant, unlabeled. First & fourth quadrant points are on the same vertical dashed segment. Portions of x axis, from the origin to each of the vertical dashed segments, are highlighted, left one labeled negative x, right one labeled, x. Equation written below: 360 degrees minus 52 degrees, = 308 degrees.

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