Use a calculator to solve the equation on the on the interval [0, 2π). Round the answer to two decimal places. cos x = 0.65?

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Well, using your calculator and the inverse cosine function, you easily find out one of the solutions:
x = arccos(0.65)
x ≈ 0.86321189 radians

So the first answer is 0.86 and that is included in all the answers above.

Now look at your unit circle and figure out where else you would have a positive cosine of 0.65. It would have to be in the 4th quadrant. It would be -0.86321189 radians, or in the range 0 to 2π, it would be:
2π - 0.86321189
≈ 5.41997341718

Answer:
C. 0.86, 5.42

As a double-check, just take the cosine of both answers and make sure you get about 0.65
cos(0.86) ≈ 0.65
cos(5.42) ≈ 0.65...Show more

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x = 0•86 , 2π - 0•86 radians (quadrants 1 and 4)
x = 0•86 , 5•42 radians...Show more