SOLUTION: A(5;5), B(-7;1), C(1;-7) are the vertices of triangle ABC which is an isosceles triangle. D(x;y) is a point in Quadrant 4 such that ABCD is a parallelogram. Calculate the area of A

Question 863143: A(5;5), B(-7;1), C(1;-7) are the vertices of triangle ABC which is an isosceles triangle. D(x;y) is a point in Quadrant 4 such that ABCD is a parallelogram. Calculate the area of ABCD correct to 3 decimal places.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Distance between two points (AB)
x1 y1 x2 y2

5 5 -7 1
d=
d=
d=
d=
d= 12.65
Distance between two points (BC)
x1 y1 x2 y2

1 -7 -7 1
d=
d=
d=
d=
d= 11.31

Distance between two points (AC)
x1 y1 x2 y2

-7 1 5 5
d=
d=
d=
d=
d= 12.65

Apply Herons formula for area of triangle
Area of triangle =
where s = 1/2 perimeter
Perimeter36.61
s=18.31
Area =
=31.004
area of parallelogram = 2 * area of triangle
=2*31.004
=62.008 sq. units
=
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