Answer: D. -37pi/9
Step-by-step explanation:
The rest of the answer choices have a reference angle of 2pi/9
The reference angle of π/9 is -37π/9 option (d) -37π/9 is correct.
It is defined as the angle formed between the terminal side and x-axis, known as the reference angle.
We have an angle of π/9
The angle -37π/9 is a reference angle of π/9 because:
= (2π+2π)-37π/9 (one complete revolution is 2π)
= (18 + 18-37)π/9
= π/9
Thus, the reference angle of π/9 is -37π/9 option (d) -37π/9 is correct.
Learn more about the reference angle here:
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