McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
4. Rectangles
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Exercise 24 Page 509

If the diagonals of a parallelogram are congruent, then it is a rectangle.

Graph:

Is It a Rectangle? Yes, see solution.

Practice makes perfect

Let's plot the given points and draw the quadrilateral on a coordinate plane.

We can use the Distance Formula to determine whether the figure is a rectangle. First, we will check if it is a parallelogram by finding the length of each side.

Side Distance Formula Simplify
Length of QT: ( - 2,2), ( 4,5) sqrt(( 4-( - 2))^2+( 5- 2)^2) sqrt(45)
Length of TS: ( 4,5), ( 6,1) sqrt(( 6- 4)^2+( 1- 5)^2) sqrt(20)
Length of RS: ( 0,- 2), ( 6,1) sqrt(( 6- 0)^2+( 1-( - 2))^2) sqrt(45)
Length of QR: ( -2,2), ( 0,-2) sqrt(( 0-( -2))^2+( - 2- 2)^2) sqrt(20)

Both pairs of opposite sides are congruent, so we know that the given quadrilateral is a parallelogram. Now, recall that if the diagonals of a parallelogram are congruent, then it is a rectangle. Let's use the Distance Formula again to find the lengths of the diagonals QS and TR.

Side Distance Formula Simplify
Length of QS: ( -2,2), ( 6,1) sqrt(( 6-( -2))^2+( 1- 2)^2) sqrt(65)
Length of TR: ( 4,5), ( 0,-2) sqrt(( 0- 4)^2+( -2- 5)^2) sqrt(65)

The diagonals of our parallelogram are congruent. Therefore, it is a rectangle.