Answer:
D(-3, -1)
Step-by-step explanation:
The given coordinates are;
A(-1, -5), B(5, -2) and (1, 1)
The coordinates and the coordinates of the point D form a trapezium
The parallel sides of the trapezium ABCD = AB and DC
The angle ∠BAD = 90°
The coordinates of the point D = Required
Let (x, y) represent the x and y-coordinates of the point D, by the given information, we get;
The slope of the line DC = The slope of the line AB
The slope of AB = (-2 - (-5))/(5 - (-1)) = 3/6 = 1/2
∴ The slope of CD, m = 1/2
From the point C(1, 1),the equation of the line CD is therefore;
y - 1 = (1/2)·(x - 1)
∴ y = x/2 - (1/2) + 1 = x/2 + 1/2
y = x/2 + 1/2
Given that ∠BAD is 90°, therefore, AD is perpendicular to DC and we have;
The slope of AD = -1/m
∴ The slope of AD = -1/(1/2) = -2
From the point A(-1, -5), the equation of the line AD is therefore;
y - (-5) = -2·(x - (-1))
y = -2·x - 2 - 5 = -2·x - 7
y = -2·x - 7
Equating both (simultaneous) values of y to find the value of x gives;
y = y, therefore;
x/2 + 1/2 = -2·x - 7
x/2 + 2·x = 5·x/2 = -7 - (1/2) = -15/2
∴ 5·x/2 = -15/2
x = (-15/2) × (2/5) = -3
x = -3
From y = -2·x - 7, and x = -3, we get;
y = -2 × (-3) - 7 = 6 - 7 = -1
The coordinates of the point D(x, y) = (-3, -1).
