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Home > CCA2 > Chapter 8 > Lesson 8.3.2 > Problem 8-155

8-155.

For each equation, find two solutions , which make the equation true. No calculator should be necessary.  

Compute without a calculator

  1.  

    Recall that  so the reference angle will be .

    In which quadrants is cosine negative? Sketch a unit circle with right triangles with angles at the origin in the second and third quadrants. What are the circular angles?

    and

    Now convert the angles into radians.

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    See part (a).

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    If , .

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    Remember the side ratios of right triangles.