Algebra-2

On the unit circle, the sign of the x- and y-coordinates determines the quadrant:  
x > 0 ,  y > 0 : First quadrant.  
x < 0 ,  y > 0 : Second quadrant.
x < 0 ,  y < 0 : Third quadrant.  
x > 0 ,  y < 0 : Fourth quadrant.  

Sine (-coordinate) is negative in the third and fourth quadrants.  

Tangent () is positive when and

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