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Sethammons · Answer 1 · 2019-07-12T23:15:14+0000

sin (x + y) = sin x cos y + sin y cos x

sin y = -4/5 and cos x = -sqrt255

so sin(x + y) = -1/4 * -3/5 + -4/5 * sqrt255
= 3/20 - 4 sqrt255/5
= (3 - 16 sqrt255) / 20 answer

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