Trigonometric graphs

Graphs

• You need to recognise and be able to sketch the graphs of the trigonometric functions sin,cos and tan
• y=sinx and y=cosx
  • y = sinx and y=cosx have the same shape
  • y = sinx is y=cosx translated by 90 to the right
  • y = cosx is symmetrical about the y-axis
  • y = sinx is symmetrical about the line x = 90
• y=tanx
  • y=tanx repeats every 180
  • There are asymptotes at -90,90,270…
  • The graph gets closer to these asymptotes but never reaches them

Sketching a trig graph

• Label the x-axis in multiples of 90
• For sin and cos label the y-axis from -1 to 1
• For tan label the y-axis from -3 to 3
• Mark some values that you know on your graph