Graphing the given point takes us to quadrant 4. Drop a perpendicular to the point (1, -1) and draw a line from the origin to the point. This line is the hypotenuse.
Let h = hypotenuse
(-1)^2 + (1)^2 = h^2
1 + 1 = h^2
2 = h^2
Taking the square root on both sides of the equation we get
sqrt{2} = h
In quadrant 4, only cosine is positive.
sine θ = -1/sqrt{2}
cos θ = 1/sqrt{2}
tan θ = -1/1
tan θ = -1
Did you follow?
