(5,-3) is in quadrant IV, so cosθ > 0 and sinθ < 0.

√(5²+(-3)²) = √34

cosθ = 5/√34 = (5√34)/34

cscθ = 1/sinθ

= 1/(-3/√34)

= -√34/3

tanθ = sinθ/cosθ = -3/5

rule:

the terminal side of θis (a,b)

--->cosθ = a/√(a^2+b^2) , sinθ = b/√(a^2+b^2) , tanθ = b/a