posted by Anonymous .
What is the exact value of cot(5(pi)/6)?
= cos(5π/6) / sin(5π/6)
= sin(π/2 - 5π/6)/ cos(π/2 - 5π/6)
Use Google, if you don't have a calculator. Type
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Then take the reciprocal of that answer, for the cotangtent.
You may recognize the answer as the square root of 3.
5 pi/6 is a 150 degree angle. The reference angle is 30 degrees, but cosine is negative in the second quadrant.