Trigonometry: Graphs and Functions

• sin is positive in the 1st and 2nd quadrant
• tan is positive in the 1st and 3rd quadrant
• cos is positive in the 1st and 4th quadrant
• subtract angle from 180 in the second quadrant
• add angle to 180 in the third quadrant
• subtract angle from 360 in the fourth quadrant
• a squared trig term has an answer in all four quadrants
• angles are normally measured anticlockwise from 0
• negative angles are measure clockwise from 0
• pi radians = 180 degrees
• convert from degrees to radians

  multiply by pi/180
• convert from radians to degrees

  multiply by 180/pi
• for points of intersections

  use y=y
• What are the key relationships between radians and degrees?


  • 2π radians = 360°
  • π radians = 180°
  • π/2 radians = 90°
• What are some common radian measures to memorize?


  • 0 radians = 0°
  • π/6 radians = 30°
  • π/4 radians = 45°
  • π/3 radians = 60°
  • π/2 radians = 90°
  • π radians = 180°
  • 2π radians = 360°
• keep trig equations in degrees until the end
• tan(x) = opposite / adjacent
• cos(x) = adjacent / hypotenuse
• for factorising, pretend trig term is not there