Part 2 4-6 please help

Find the value of the cosine for angle a

Aball is dropped from a height of 10m above the ground. it bounce to 90% of its previous height on each bounce. what is the approximate height that the ball bounce to the fourth bounce?

Find the equation of the ellipse with the following properties. the ellipse with foci at (0, 6) and (0, -6); y-intercepts (0, 8) and (0, -8).edit: the answer is x^2 over 28 + y^2 over 64 = 1