document.write( "Question 958282: find sin(x+y) if sin x=2/3 and sin y= -1/3 \n" ); document.write( "
Algebra.Com's Answer #585649 by jsmallt9(3758)\"\" \"About 
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This problem cannot be solved without additional information. This is so because
  • To find sin(x+y) we will use the identity:
    \n" ); document.write( "sin(x+y) = sin(x)cos(y) + cos(x)sin(y)
  • The identity requires cos(x) and cos(y).
  • But without information telling us the quadrant in which x and y terminate, we cannot find these cos's.
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