The equations

and

are really the same, we're just setting
, or
.

So we get

Answer:
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The length of the hypotenuse = √(-3^2 +1^2) = √10
The point -3,1 tell us the length of y is 1 and the length of x is 3.
This would make opposite = 1 and adjacent = -3
Sinθ = opposite/hypotenuse = 1/√10 = √10/10
Cosθ = adjacent/hypotenuse = -3/√10 = - 3√10/10
Tanθ = opposite/adjacent = 1/-3 = -1/3