2 answers
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no idea what "−3–√" means
tan π/6 = cot π/3 = 1/√3
cot π/6 = tan π/3 = √3
so,
tan 11π/6 = -1/√3
cot 7π/6 = √3
and so on. Draw the angles in the proper quadrant to see.
tanθ = y/x
cotθ = x/y