consider angles in standard position.
sinθ = y/r
cosθ = x/r
tanθ = y/x
so, sinθ < 0 when y < 0 -- QIII,QIV
now do the others
In which quadrants is sin(theta) < 0?
In which quadrants is cos(theta > 0?
In which quadrants is tan(theta) < 0?
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