If sin x° = a, which of the following must be true for all values of x?

Correct answer: C. cos (90o - xo ) = a

  • A. cos x° = a
  • B. sin (90o - xo) = a
  • C. cos (90o - xo ) = a
  • D. sin (x2)° = a2

Explanation

Choice C is correct. The sine of an angle is equal to the cosine of the angle's complement. This relationship can be expressed by the equation sin x° = cos (90° − x°). Therefore, if sin x° = a, then cos (90° − x°) must also be equal to a.

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