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The following are all angle measures (in radians, rounded to the nearest hundredth) whose cosine is 
-0.26.
Which is the principal value of 
cos^(-1)(-0.26) ?
Choose 1 answer:
(A) -17.02
(B) -10.73
(C) -4.45
(D) 1.83

The following are all angle measures (in radians, rounded to the nearest hundredth) whose cosine is 0.26 \mathbf{- 0 . 2 6} .\newlineWhich is the principal value of cos1(0.26) \cos ^{-1}(-0.26) ?\newlineChoose 11 answer:\newline(A) 17-17.0202\newline(B) 10-10.7373\newline(C) 4-4.4545\newline(D) 11.8383

Full solution

Q. The following are all angle measures (in radians, rounded to the nearest hundredth) whose cosine is 0.26 \mathbf{- 0 . 2 6} .\newlineWhich is the principal value of cos1(0.26) \cos ^{-1}(-0.26) ?\newlineChoose 11 answer:\newline(A) 17-17.0202\newline(B) 10-10.7373\newline(C) 4-4.4545\newline(D) 11.8383
  1. Consider Range of Cosine Inverse: To find the principal value of the inverse cosine function, we need to consider the range of the principal values for the cosine inverse, which is from 00 to π\pi for positive values and from π-\pi to 00 for negative values. Since 0.26-0.26 is a negative value, we are looking for an angle in the third or fourth quadrant where the cosine is negative.
  2. Identify Quadrant for Principal Value: The principal value of cos1(0.26)\cos^{-1}(-0.26) will be in the second quadrant because cosine is negative there, and the range of the inverse cosine function for negative values is from 00 to π\pi.
  3. Use Calculator for Computation: To find the principal value, we can use a calculator to compute cos1(0.26)\cos^{-1}(-0.26). Make sure the calculator is set to radian mode since the answers are given in radians.
  4. Calculate Principal Value: Using a calculator, we find that cos1(0.26)1.83\cos^{-1}(-0.26) \approx 1.83 radians.
  5. Verify within Range: Since 1.831.83 radians is within the range of 00 to π\pi, it is the principal value for cos1(0.26)\cos^{-1}(-0.26). Therefore, the correct answer is (D) 1.831.83.

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