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Home > PC3 > Chapter 5 > Lesson 5.2.5 > Problem 5-124


Sylvie needs to solve on a math test. She knows that is the inverse function for cosine, so she applies this function to both sides of the equation. This gives her . But when her test is returned, she learns she earned only partial credit on the problem.  

  1. Why did Sylvie only get partial credit?

    There are multiple solutions.

  2. What should Sylvie have answered to receive full credit? Explain your answer.

    Sylvie needs to include all the solutions, which she can get using a graph or unit circle.