Question

D(5, 7), E(4, 3), and F(8, 2) form the vertices of a triangle. What is
m DEF?

Answer 1

area?

Answer 2

...

Answer 3

To find
m\(\angle\)DEF
calculate the slopes of DE and EF and examine the values.
To find slopes, use the following formula:
slope =\(\Large \frac{y_2-y_1}{x_2-x_1}\)
If the product of two slopes equal -1, then the two lines are perpendicular to each other.