Let in ∆ABC, A(1,1), B(x₁, y₁) and C(x₂, y₂).

Let D(-2, 3) and E(5, 2) be the midpoints of sides AB and AC respectively.

By midpoint formula.

x = , y =

For mid point D (-2, 3) of side AB,

-2 = , 3 =

1 + x₁ = -4 and 1 + y₁ = 6

x₁ = -5 and y₁ = 5

∴ B ( x₁, y₁) ≡ (-5, 5)

For midpoint E(5, 2) of side AC,

5 = , 2 =

1 + x₂ = 10 and = 4

∴ x₂ = 9 and = 3

∴ C(x₂, y₂) ≡ (9, 3)

Hence other two vertices are B (-5, 5) and C(9, 3)