Determine the quadrant in which theta lies: sin theta<0 and cos theta<0?

1 Answer
KillerBunny
Jun 20, 2018

Third quadrant

Explanation:

Since the cosine is related to the #x# coordinate of a point and the sine is related to the #y# coordinate, we need a point #P=(x,y)# with both #x<0# and #y<0#.

This happens in the third quadrant, since we have:

  • First quadrant: #x>0# and #y>0#
  • Second quadrant: #x<0# and #y>0#
  • Third quadrant: #x<0# and #y<0#
  • Fourth quadrant: #x>0# and #y>0#
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