Helppp pls :)

Find the value of the cosine for angle a

A, b, c, and d have the coordinates (-8, 1), (-2, 4), (-3, -1), and (-6, 5), respectively. which sentence about the points is true? a. a, b, c, and d lie on the same line. b. and are perpendicular lines. c. and are parallel lines. d. and are intersecting lines but are not perpendicular. e. and are parallel lines.

Simplify the expression and find the missing terms. the simplest form of has in the numerator and in the denominator.