Answer
-1/√50
Explanation
We are going to take the angle ∅ to at the origin (at point (0, 0)).
The point (7, -1) means 7 units to the right and 1 unit downwards (negative side of y-axis).
This makes a right triangle. The hypotenuse √(7²+1²) = √50
Now,
sine = opposite/hypotenuse
= 1/√50
Angle ∅ is in the 4th quadrilant where the sine is egative.
so, the exact answer of sin∅ = -1/√50
