Please help ASAP! Thank you!

Find the value of the cosine for angle a

Find the solution(s) to the system of equations. select all that apply y=x^2-1 y=2x-2

5. which description does not guarantee that a quadrilateral is a squar ajo is a parallelogram with perpendicular diagonals 0% has all sides congruent and all angles congruent o has all right angles and has all sides congruent 10% is both a rectangle and a rhombus 30%