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Answer:
 sin(Z) = 3/5
 cos(Z) = 4/5
Explanation:
The mnemonic SOH CAH TOA reminds you how to do this.
 Sin = Opposite/Hypotenuse
 sin(Z) = XY/XZ = 9/15
 sin(Z) = 3/5 . . . . . reduced fraction
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 Cos = Adjacent/Hypotenuse
 cos(Z) = YZ/XZ = 12/15
 cos(Z) = 4/5 . . . . . reduced fraction