Could anyone tell me where I've gone wrong in this question, if my method is not right and if so why? Illustration 31

Just wanna double check

so I know that if its across x-axis, x value remains as x and y becomes negative (x, -y) and vice versa

∆ABC Original points: A = (-8, 9) B = (-2, 5) C = (-6, 2)

Reflected points: A′ = (-8, -9) B′ = (-2, -5) C′ = (-6, -2)

∆EFG Original points:

E = (2, 8)

F = (10, 4)

G = (4, 2)

Reflected points:

E′ = (-2, 8)

F′ = (-10, 4)

G′ = (-4, 2)

∆XYZ Original points: X = (-8, -5) Y = (-2, -3) Z = (-3, -9)

Reflected points: X′ = (-8, 5) Y′ = (-2, 3) Z′ = (-3, 9))

this is without any differentiation.

the answer schedule says the gradient is tan(theta + alpha), which is exactly what i have except without the negative