Answer: Yes the diagonals are perpendicular
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Step-by-step explanation:
The diagonals connect the non-adjacent vertices.
The two diagonals in this case are CE and DF.
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Let's use the slope formula to compute the slope of segment CE.
C = (0,0)
E = (9,6)

Segment CE has a slope of 2/3.
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Now we'll find the slope of diagonal DF.
D = (8,1)
F = (4,7)

Segment DF has slope -3/2.
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Summary:
- Diagonal CE has slope 2/3
- Diagonal DF has slope -3/2
The product of those slopes is (2/3)*(-3/2) = -6/6 = -1
The slopes having a product of -1 is sufficient evidence to show the diagonals being perpendicular. The two diagonals meet up to form a 90 degree angle. This property is true of any kite in geometry.
Notice how -3/2 is the negative reciprocal of 2/3, and vice versa.