text: # trig
  
  If sin = 4/5 with A in QII, and sin B = -3/5 with B in QIV find cos(A-B)
  
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  1. cos(A-B)= cosAcosB+sinAsinB
  
  If sinA = 4/5 in QII
  draw you triangle in QII, and find the third side.
  The third side is 3. (Do the same thing for sin B= -3/5
  Plug in:
  cosAcosB-sinAsinB
  =(-3/5)*(4/5)+(4/5)*(-3/5)
  =(-12/25) -(-12/25)
  =-24/25
  
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  2. 53. the longest side is 55 cm. find the length of the shortest side
  
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