Signs of trig functions

Solomon Xie
All Math Before College
1 min readJan 27, 2019

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Before solving a trig equation, need look at the sign of the equation, AND identify which one or multiple quadrants will the solutions land in.

  • Quadrant I: All trig functions are POSITIVE.
  • Quadrant II: Only sin(x) is POSITIVE, others are all NEGATIVE.
  • Quadrant III: Only tan(x) is POSITIVE, others are all NEGATIVE.
  • Quadrant IV: Only cos(x) is POSITIVE, others are all NEGATIVE.

e.g.
sin(x) = 123 have a positive sign, so it will have two solutions: one in Quadrant I, another be Quadrant II.
-cos(2x+3)=234have a negative sign, so it'll have two solutions in Quadrant IIand Quadrant III.

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Solomon Xie
All Math Before College

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