trig

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Give exact answers
Sin(11pi/8)
so this is sin(pi/4+pi/3)
sin(pi/4)*cos(pi/3)+cos(pi/3)*sin(pi/4)
rad2/2*1/2+1/2*rad2/2

which gives me rad2+rad2 all over 4 ...i don't know y im getting it wrong

  • trig -

    pi/4 + pi/3 does NOT equal 11 pi/8
    It equals 7 pi/12

    sin (11pi/8) = -sin3pi/8
    = -sin[(1/2)3pi/4]
    Now use the "sine half angle" formula
    = -sqrt[(1/2)(1-cos3pi/4)]
    = -sqrt[(1/2)(1+(sqrt2)/2)]

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