4. Rectangles
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If the diagonals of a parallelogram are congruent, then it is a rectangle.
Graph:
Is It a Rectangle? No, see solution.
Let's plot the given points and draw the quadrilateral on a coordinate plane.
We can use the Slope Formula to determine whether the figure is a rectangle. Let's find the slope of each side.
| Side | Slope Formula | Simplify |
|---|---|---|
| Slope of HG, ( - 7,7), ( 1,8) | 8- 7/1-( - 7) | 1/8 |
| Slope of GK, ( 1,8), ( 2, 2) | 2- 8/2- 1 | - 6 |
| Slope of JK, ( - 6, 1), ( 2, 2) | 2- 1/2-( - 6) | 1/8 |
| Slope of HJ, ( - 7,7), ( - 6, 1) | 1- 7/- 6-( - 7) | - 6 |
The slopes of the opposite sides of our quadrilateral are equal, so both pairs of opposite sides are parallel. Therefore, we know that the quadrilateral is a parallelogram. We can also tell that the consecutive side are not perpendicular, as their slopes are not opposite reciprocals. - 6 * 1/8 ≠ -1 Therefore, our quadrilateral is not a rectangle, as its consecutive sides are not perpendicular.