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If sinx=3/5,cosy=-12/13,where x and y both lie in 2nd quad.Find the value os sin(x+y).

  • math -

    luckily, you have nice easy 3-4-5 and 5-12-13 triangles.

    cosx = -4/5
    siny = 5/13

    sin(x+y) = (3/5)(-12/13) + (-4/5)(5/13) = -56/65

    reasonable, since (x+y) will be in QIII or QIV

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