Answer each of the following questions in one word or one sentence or as per exact requirement of the question:

Write the principal value of cos–1(cos 680°).


Given cos-1 (cos 680°)


= cos-1 (cos (720° - 40°))


= cos-1 (cos (2 × 360° - 40°))


= cos-1 (cos 40°)


= 40°


cos-1 (cos 680°) = 40°


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